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 $177.51   9.662%   $194.661   $194.66   $194.65   $194.70  
  Purchase #2 $121.39   3.756%   $125.9494   $125.95   $125.95   $125.90  
  Purchase #3 $150.62   3.320%   $155.6206   $155.62   $155.60   $155.60  
  Purchase #4 $202.45   11.831%   $226.4019   $226.40   $226.40   $226.40  
  Purchase #5 $85.42   6.824%   $91.2491   $91.25   $91.25   $91.20  
  Purchase #6 $97.75   10.241%   $107.7606   $107.76   $107.75   $107.80  
  Purchase #7 $188.39   11.598%   $210.2395   $210.24   $210.25   $210.20  
  7 purchase totals = $1,023.53       $1,111.8821   $1,111.88   $1,111.85   $1,111.80