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 $91.85   5.398%   $96.8081   $96.81   $96.80   $96.80  
  Purchase #2 $10.38   9.221%   $11.3371   $11.34   $11.35   $11.30  
  Purchase #3 $49.83   8.758%   $54.1941   $54.19   $54.20   $54.20  
  Purchase #4 $45.79   5.747%   $48.4216   $48.42   $48.40   $48.40  
  Purchase #5 $54.74   5.278%   $57.6292   $57.63   $57.65   $57.60  
  Purchase #6 $245.85   7.789%   $264.9993   $265.00   $265.00   $265.00  
  Purchase #7 $194.25   3.457%   $200.9652   $200.97   $200.95   $201.00  
  7 purchase totals = $692.69       $734.3546   $734.36   $734.35   $734.30