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 $174.77   11.598%   $195.0398   $195.04   $195.05   $195.00  
  Purchase #2 $36.73   4.403%   $38.3472   $38.35   $38.35   $38.30  
  Purchase #3 $131.47   6.810%   $140.4231   $140.42   $140.40   $140.40  
  Purchase #4 $210.64   6.349%   $224.0135   $224.01   $224.00   $224.00  
  Purchase #5 $63.64   7.211%   $68.2291   $68.23   $68.25   $68.20  
  Purchase #6 $174.52   6.512%   $185.8847   $185.88   $185.90   $185.90  
  Purchase #7 $169.44   12.650%   $190.8742   $190.87   $190.85   $190.90  
  7 purchase totals = $961.21       $1,042.8116   $1,042.80   $1,042.80   $1,042.70