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 $60.52   12.283%   $67.9537   $67.95   $67.95   $68.00  
  Purchase #2 $146.54   3.395%   $151.515   $151.52   $151.50   $151.50  
  Purchase #3 $42.46   13.540%   $48.2091   $48.21   $48.20   $48.20  
  Purchase #4 $209.44   3.325%   $216.4039   $216.40   $216.40   $216.40  
  Purchase #5 $92.47   13.525%   $104.9766   $104.98   $105.00   $105.00  
  Purchase #6 $246.76   6.665%   $263.2066   $263.21   $263.20   $263.20  
  Purchase #7 $169.53   13.757%   $192.8522   $192.85   $192.85   $192.90  
  7 purchase totals = $967.72       $1,045.1171   $1,045.12   $1,045.10   $1,045.20