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 $76.58   11.297%   $85.2312   $85.23   $85.25   $85.20  
  Purchase #2 $120.36   5.668%   $127.182   $127.18   $127.20   $127.20  
  Purchase #3 $74.77   12.407%   $84.0467   $84.05   $84.05   $84.00  
  Purchase #4 $203.56   3.596%   $210.88   $210.88   $210.90   $210.90  
  Purchase #5 $247.53   12.167%   $277.647   $277.65   $277.65   $277.60  
  Purchase #6 $184.56   11.560%   $205.8951   $205.90   $205.90   $205.90  
  Purchase #7 $153.51   12.859%   $173.2499   $173.25   $173.25   $173.20  
  7 purchase totals = $1,060.87       $1,164.1319   $1,164.14   $1,164.20   $1,164.00