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 $44.38   6.688%   $47.3481   $47.35   $47.35   $47.30  
  Purchase #2 $62.86   9.398%   $68.7676   $68.77   $68.75   $68.80  
  Purchase #3 $67.27   10.446%   $74.297   $74.30   $74.30   $74.30  
  Purchase #4 $183.49   9.662%   $201.2188   $201.22   $201.20   $201.20  
  Purchase #5 $195.80   13.305%   $221.8512   $221.85   $221.85   $221.90  
  Purchase #6 $228.93   9.768%   $251.2919   $251.29   $251.30   $251.30  
  Purchase #7 $77.65   12.281%   $87.1862   $87.19   $87.20   $87.20  
  7 purchase totals = $860.38       $951.9608   $951.97   $951.95   $952.00