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 $46.75   7.329%   $50.1763   $50.18   $50.20   $50.20  
  Purchase #2 $173.85   13.297%   $196.9668   $196.97   $196.95   $197.00  
  Purchase #3 $96.82   10.601%   $107.0839   $107.08   $107.10   $107.10  
  Purchase #4 $220.46   7.638%   $237.2987   $237.30   $237.30   $237.30  
  Purchase #5 $214.79   12.198%   $240.9901   $240.99   $241.00   $241.00  
  Purchase #6 $185.90   9.778%   $204.0773   $204.08   $204.10   $204.10  
  Purchase #7 $23.71   9.317%   $25.9191   $25.92   $25.90   $25.90  
  7 purchase totals = $962.28       $1,062.5122   $1,062.52   $1,062.55   $1,062.60