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 $153.28   13.698%   $174.2763   $174.28   $174.30   $174.30  
  Purchase #2 $85.90   9.485%   $94.0476   $94.05   $94.05   $94.00  
  Purchase #3 $26.64   8.140%   $28.8085   $28.81   $28.80   $28.80  
  Purchase #4 $230.57   7.528%   $247.9273   $247.93   $247.95   $247.90  
  Purchase #5 $173.82   11.224%   $193.3296   $193.33   $193.35   $193.30  
  Purchase #6 $41.33   11.850%   $46.2276   $46.23   $46.25   $46.20  
  Purchase #7 $82.91   9.564%   $90.8395   $90.84   $90.85   $90.80  
  7 purchase totals = $794.45       $875.4564   $875.47   $875.55   $875.30