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 $68.69   7.654%   $73.9475   $73.95   $73.95   $73.90  
  Purchase #2 $134.41   8.446%   $145.7623   $145.76   $145.75   $145.80  
  Purchase #3 $35.93   8.398%   $38.9474   $38.95   $38.95   $38.90  
  Purchase #4 $202.77   11.714%   $226.5225   $226.52   $226.50   $226.50  
  Purchase #5 $27.66   13.446%   $31.3792   $31.38   $31.40   $31.40  
  Purchase #6 $229.33   6.842%   $245.0208   $245.02   $245.00   $245.00  
  Purchase #7 $185.29   6.425%   $197.1949   $197.19   $197.20   $197.20  
  7 purchase totals = $884.08       $958.7746   $958.77   $958.75   $958.70