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 $41.75   12.641%   $47.0276   $47.03   $47.05   $47.00  
  Purchase #2 $119.52   3.755%   $124.008   $124.01   $124.00   $124.00  
  Purchase #3 $234.44   12.329%   $263.3441   $263.34   $263.35   $263.30  
  Purchase #4 $173.89   9.245%   $189.9661   $189.97   $189.95   $190.00  
  Purchase #5 $135.71   3.866%   $140.9565   $140.96   $140.95   $141.00  
  Purchase #6 $174.26   4.362%   $181.8612   $181.86   $181.85   $181.90  
  Purchase #7 $15.46   7.749%   $16.658   $16.66   $16.65   $16.70  
  7 purchase totals = $895.03       $963.8215   $963.83   $963.80   $963.90