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 $181.71   10.832%   $201.3928   $201.39   $201.40   $201.40  
  Purchase #2 $53.46   13.118%   $60.4729   $60.47   $60.45   $60.50  
  Purchase #3 $157.57   10.435%   $174.0124   $174.01   $174.00   $174.00  
  Purchase #4 $232.52   5.865%   $246.1573   $246.16   $246.15   $246.20  
  Purchase #5 $96.47   3.387%   $99.7374   $99.74   $99.75   $99.70  
  Purchase #6 $90.36   7.832%   $97.437   $97.44   $97.45   $97.40  
  Purchase #7 $47.93   11.479%   $53.4319   $53.43   $53.45   $53.40  
  7 purchase totals = $860.02       $932.6417   $932.64   $932.65   $932.60