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 $52.70   11.858%   $58.9492   $58.95   $58.95   $58.90  
  Purchase #2 $172.47   10.585%   $190.7259   $190.73   $190.75   $190.70  
  Purchase #3 $234.65   13.836%   $267.1162   $267.12   $267.10   $267.10  
  Purchase #4 $102.84   3.245%   $106.1772   $106.18   $106.20   $106.20  
  Purchase #5 $147.71   5.262%   $155.4825   $155.48   $155.50   $155.50  
  Purchase #6 $121.34   9.860%   $133.3041   $133.30   $133.30   $133.30  
  Purchase #7 $128.71   4.269%   $134.2046   $134.20   $134.20   $134.20  
  7 purchase totals = $960.42       $1,045.9597   $1,045.96   $1,046.00   $1,045.90