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 $84.74   12.438%   $95.28   $95.28   $95.30   $95.30  
  Purchase #2 $84.30   12.840%   $95.1241   $95.12   $95.10   $95.10  
  Purchase #3 $218.72   11.478%   $243.8247   $243.82   $243.80   $243.80  
  Purchase #4 $200.32   9.209%   $218.7675   $218.77   $218.75   $218.80  
  Purchase #5 $112.43   3.331%   $116.175   $116.18   $116.20   $116.20  
  Purchase #6 $27.43   9.242%   $29.9651   $29.97   $29.95   $30.00  
  Purchase #7 $233.36   5.647%   $246.5378   $246.54   $246.55   $246.50  
  7 purchase totals = $961.30       $1,045.6742   $1,045.68   $1,045.65   $1,045.70