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 $118.46   13.603%   $134.5741   $134.57   $134.55   $134.60  
  Purchase #2 $174.43   12.206%   $195.7209   $195.72   $195.70   $195.70  
  Purchase #3 $107.43   12.831%   $121.2143   $121.21   $121.20   $121.20  
  Purchase #4 $243.30   9.182%   $265.6398   $265.64   $265.65   $265.60  
  Purchase #5 $178.47   4.641%   $186.7528   $186.75   $186.75   $186.80  
  Purchase #6 $152.44   11.156%   $169.4462   $169.45   $169.45   $169.40  
  Purchase #7 $58.89   5.201%   $61.9529   $61.95   $61.95   $62.00  
  7 purchase totals = $1,033.42       $1,135.3010   $1,135.29   $1,135.25   $1,135.30