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 $106.80   11.372%   $118.9453   $118.95   $118.95   $118.90  
  Purchase #2 $127.52   9.229%   $139.2888   $139.29   $139.30   $139.30  
  Purchase #3 $212.42   6.629%   $226.5013   $226.50   $226.50   $226.50  
  Purchase #4 $78.84   7.650%   $84.8713   $84.87   $84.85   $84.90  
  Purchase #5 $245.65   4.198%   $255.9624   $255.96   $255.95   $256.00  
  Purchase #6 $129.51   11.549%   $144.4671   $144.47   $144.45   $144.50  
  Purchase #7 $247.65   9.604%   $271.4343   $271.43   $271.45   $271.40  
  7 purchase totals = $1,148.39       $1,241.4705   $1,241.47   $1,241.45   $1,241.50