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 $167.60   5.323%   $176.5213   $176.52   $176.50   $176.50  
  Purchase #2 $142.97   6.156%   $151.7712   $151.77   $151.75   $151.80  
  Purchase #3 $157.26   11.627%   $175.5446   $175.54   $175.55   $175.50  
  Purchase #4 $232.27   3.831%   $241.1683   $241.17   $241.15   $241.20  
  Purchase #5 $174.85   4.546%   $182.7987   $182.80   $182.80   $182.80  
  Purchase #6 $169.85   11.728%   $189.77   $189.77   $189.75   $189.80  
  Purchase #7 $189.87   13.409%   $215.3297   $215.33   $215.35   $215.30  
  7 purchase totals = $1,234.67       $1,332.9038   $1,332.90   $1,332.85   $1,332.90