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 $71.67   5.581%   $75.6699   $75.67   $75.65   $75.70  
  Purchase #2 $9.92   8.297%   $10.7431   $10.74   $10.75   $10.70  
  Purchase #3 $142.66   5.293%   $150.211   $150.21   $150.20   $150.20  
  Purchase #4 $143.78   5.262%   $151.3457   $151.35   $151.35   $151.30  
  Purchase #5 $172.86   3.300%   $178.5644   $178.56   $178.55   $178.60  
  Purchase #6 $122.98   6.720%   $131.2443   $131.24   $131.25   $131.20  
  Purchase #7 $118.74   8.809%   $129.1998   $129.20   $129.20   $129.20  
  7 purchase totals = $782.61       $826.9782   $826.97   $826.95   $826.90