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 $160.68   5.591%   $169.6636   $169.66   $169.65   $169.70  
  Purchase #2 $203.48   3.377%   $210.3515   $210.35   $210.35   $210.40  
  Purchase #3 $36.70   5.175%   $38.5992   $38.60   $38.60   $38.60  
  Purchase #4 $229.85   9.285%   $251.1916   $251.19   $251.20   $251.20  
  Purchase #5 $46.50   4.374%   $48.5339   $48.53   $48.55   $48.50  
  Purchase #6 $170.82   5.501%   $180.2168   $180.22   $180.20   $180.20  
  Purchase #7 $219.65   7.617%   $236.3807   $236.38   $236.40   $236.40  
  7 purchase totals = $1,067.68       $1,134.9373   $1,134.93   $1,134.95   $1,135.00