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 $191.99   5.310%   $202.1847   $202.18   $202.20   $202.20  
  Purchase #2 $199.81   13.833%   $227.4497   $227.45   $227.45   $227.40  
  Purchase #3 $89.29   11.224%   $99.3119   $99.31   $99.30   $99.30  
  Purchase #4 $52.31   5.812%   $55.3503   $55.35   $55.35   $55.40  
  Purchase #5 $102.52   5.163%   $107.8131   $107.81   $107.80   $107.80  
  Purchase #6 $160.79   5.855%   $170.2043   $170.20   $170.20   $170.20  
  Purchase #7 $240.33   13.318%   $272.3371   $272.34   $272.35   $272.30  
  7 purchase totals = $1,037.04       $1,134.6511   $1,134.64   $1,134.65   $1,134.60