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 $60.95   11.596%   $68.0178   $68.02   $68.00   $68.00  
  Purchase #2 $149.34   9.179%   $163.0479   $163.05   $163.05   $163.00  
  Purchase #3 $34.75   3.608%   $36.0038   $36.00   $36.00   $36.00  
  Purchase #4 $230.38   10.705%   $255.0422   $255.04   $255.05   $255.00  
  Purchase #5 $74.97   3.662%   $77.7154   $77.72   $77.70   $77.70  
  Purchase #6 $201.71   4.499%   $210.7849   $210.78   $210.80   $210.80  
  Purchase #7 $22.32   10.365%   $24.6335   $24.63   $24.65   $24.60  
  7 purchase totals = $774.42       $835.2455   $835.24   $835.25   $835.10