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 $187.55   3.837%   $194.7463   $194.75   $194.75   $194.70  
  Purchase #2 $37.40   10.416%   $41.2956   $41.30   $41.30   $41.30  
  Purchase #3 $62.52   9.573%   $68.505   $68.51   $68.50   $68.50  
  Purchase #4 $87.64   9.564%   $96.0219   $96.02   $96.00   $96.00  
  Purchase #5 $212.64   6.700%   $226.8869   $226.89   $226.90   $226.90  
  Purchase #6 $104.42   6.245%   $110.941   $110.94   $110.95   $110.90  
  Purchase #7 $53.82   7.811%   $58.0239   $58.02   $58.00   $58.00  
  7 purchase totals = $745.99       $796.4206   $796.43   $796.40   $796.30