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 $12.82   8.829%   $13.9519   $13.95   $13.95   $14.00  
  Purchase #2 $178.49   8.420%   $193.5189   $193.52   $193.50   $193.50  
  Purchase #3 $219.35   3.593%   $227.2312   $227.23   $227.25   $227.20  
  Purchase #4 $157.31   4.554%   $164.4739   $164.47   $164.45   $164.50  
  Purchase #5 $117.42   10.232%   $129.4344   $129.43   $129.45   $129.40  
  Purchase #6 $235.48   10.658%   $260.5775   $260.58   $260.60   $260.60  
  Purchase #7 $138.26   5.244%   $145.5104   $145.51   $145.50   $145.50  
  7 purchase totals = $1,059.13       $1,134.6982   $1,134.69   $1,134.70   $1,134.70