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 $110.45   13.858%   $125.7562   $125.76   $125.75   $125.80  
  Purchase #2 $58.84   8.150%   $63.6355   $63.64   $63.65   $63.60  
  Purchase #3 $120.33   10.815%   $133.3437   $133.34   $133.35   $133.30  
  Purchase #4 $217.82   9.653%   $238.8462   $238.85   $238.85   $238.80  
  Purchase #5 $159.48   13.270%   $180.643   $180.64   $180.65   $180.60  
  Purchase #6 $159.64   6.185%   $169.5137   $169.51   $169.50   $169.50  
  Purchase #7 $102.35   3.384%   $105.8135   $105.81   $105.80   $105.80  
  7 purchase totals = $928.91       $1,017.5518   $1,017.55   $1,017.55   $1,017.40