Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $112.65   5.651%   $119.0159   $119.02   $119.00   $119.00  
  Purchase #2 $141.97   7.244%   $152.2543   $152.25   $152.25   $152.30  
  Purchase #3 $215.69   9.141%   $235.4062   $235.41   $235.40   $235.40  
  Purchase #4 $174.35   3.748%   $180.8846   $180.88   $180.90   $180.90  
  Purchase #5 $214.58   5.104%   $225.5322   $225.53   $225.55   $225.50  
  Purchase #6 $156.49   7.620%   $168.4145   $168.41   $168.40   $168.40  
  Purchase #7 $132.85   6.275%   $141.1863   $141.19   $141.20   $141.20  
  7 purchase totals = $1,148.58       $1,222.6940   $1,222.69   $1,222.70   $1,222.70