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 $169.47   5.352%   $178.54   $178.54   $178.55   $178.50  
  Purchase #2 $171.67   10.834%   $190.2687   $190.27   $190.25   $190.30  
  Purchase #3 $223.70   9.519%   $244.994   $244.99   $245.00   $245.00  
  Purchase #4 $23.86   9.480%   $26.1219   $26.12   $26.10   $26.10  
  Purchase #5 $75.55   9.874%   $83.0098   $83.01   $83.00   $83.00  
  Purchase #6 $121.71   11.470%   $135.6701   $135.67   $135.65   $135.70  
  Purchase #7 $110.38   5.525%   $116.4785   $116.48   $116.50   $116.50  
  7 purchase totals = $896.34       $975.0830   $975.08   $975.05   $975.10