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 $96.38   5.207%   $101.3985   $101.40   $101.40   $101.40  
  Purchase #2 $187.92   12.516%   $211.4401   $211.44   $211.45   $211.40  
  Purchase #3 $33.88   12.195%   $38.0117   $38.01   $38.00   $38.00  
  Purchase #4 $205.80   12.861%   $232.2679   $232.27   $232.25   $232.30  
  Purchase #5 $203.34   6.323%   $216.1972   $216.20   $216.20   $216.20  
  Purchase #6 $64.27   13.868%   $73.183   $73.18   $73.20   $73.20  
  Purchase #7 $236.53   7.387%   $254.0025   $254.00   $254.00   $254.00  
  7 purchase totals = $1,028.12       $1,126.5009   $1,126.50   $1,126.50   $1,126.50