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 $207.86   11.523%   $231.8117   $231.81   $231.80   $231.80  
  Purchase #2 $161.95   5.712%   $171.2006   $171.20   $171.20   $171.20  
  Purchase #3 $132.57   8.671%   $144.0651   $144.07   $144.05   $144.10  
  Purchase #4 $87.77   9.843%   $96.4092   $96.41   $96.40   $96.40  
  Purchase #5 $142.62   4.620%   $149.209   $149.21   $149.20   $149.20  
  Purchase #6 $200.25   5.209%   $210.681   $210.68   $210.70   $210.70  
  Purchase #7 $99.62   11.407%   $110.9837   $110.98   $111.00   $111.00  
  7 purchase totals = $1,032.64       $1,114.3603   $1,114.36   $1,114.35   $1,114.40