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 $34.29   5.711%   $36.2483   $36.25   $36.25   $36.20  
  Purchase #2 $246.27   12.692%   $277.5266   $277.53   $277.55   $277.50  
  Purchase #3 $215.91   11.666%   $241.0981   $241.10   $241.10   $241.10  
  Purchase #4 $65.65   7.864%   $70.8127   $70.81   $70.80   $70.80  
  Purchase #5 $110.41   5.170%   $116.1182   $116.12   $116.10   $116.10  
  Purchase #6 $150.82   10.855%   $167.1915   $167.19   $167.20   $167.20  
  Purchase #7 $82.84   10.130%   $91.2317   $91.23   $91.25   $91.20  
  7 purchase totals = $906.19       $1,000.2271   $1,000.23   $1,000.25   $1,000.10