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 $111.53   12.233%   $125.1735   $125.17   $125.15   $125.20  
  Purchase #2 $58.64   6.689%   $62.5624   $62.56   $62.55   $62.60  
  Purchase #3 $80.48   4.170%   $83.836   $83.84   $83.85   $83.80  
  Purchase #4 $116.92   12.209%   $131.1948   $131.19   $131.20   $131.20  
  Purchase #5 $31.52   13.656%   $35.8244   $35.82   $35.80   $35.80  
  Purchase #6 $8.42   13.777%   $9.58   $9.58   $9.60   $9.60  
  Purchase #7 $18.57   4.733%   $19.4489   $19.45   $19.45   $19.40  
  7 purchase totals = $426.08       $467.6200   $467.61   $467.60   $467.60