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 $45.85   5.195%   $48.2319   $48.23   $48.25   $48.20  
  Purchase #2 $246.77   4.728%   $258.4373   $258.44   $258.45   $258.40  
  Purchase #3 $189.25   4.380%   $197.5392   $197.54   $197.55   $197.50  
  Purchase #4 $156.45   5.291%   $164.7278   $164.73   $164.75   $164.70  
  Purchase #5 $68.33   12.637%   $76.9649   $76.96   $76.95   $77.00  
  Purchase #6 $238.29   7.368%   $255.8472   $255.85   $255.85   $255.80  
  Purchase #7 $39.50   9.308%   $43.1767   $43.18   $43.20   $43.20  
  7 purchase totals = $984.44       $1,044.9250   $1,044.93   $1,045.00   $1,044.80