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 $84.66   12.872%   $95.5574   $95.56   $95.55   $95.60  
  Purchase #2 $25.59   6.670%   $27.2969   $27.30   $27.30   $27.30  
  Purchase #3 $206.31   10.531%   $228.0365   $228.04   $228.05   $228.00  
  Purchase #4 $226.42   12.111%   $253.8417   $253.84   $253.85   $253.80  
  Purchase #5 $243.25   8.646%   $264.2814   $264.28   $264.30   $264.30  
  Purchase #6 $175.66   11.256%   $195.4323   $195.43   $195.45   $195.40  
  Purchase #7 $180.52   5.383%   $190.2374   $190.24   $190.25   $190.20  
  7 purchase totals = $1,142.41       $1,254.6836   $1,254.69   $1,254.75   $1,254.60