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 $191.40   5.791%   $202.484   $202.48   $202.50   $202.50  
  Purchase #2 $86.77   5.627%   $91.6525   $91.65   $91.65   $91.70  
  Purchase #3 $38.39   4.252%   $40.0223   $40.02   $40.00   $40.00  
  Purchase #4 $108.65   10.347%   $119.892   $119.89   $119.90   $119.90  
  Purchase #5 $195.77   11.844%   $218.957   $218.96   $218.95   $219.00  
  Purchase #6 $187.64   4.244%   $195.6034   $195.60   $195.60   $195.60  
  Purchase #7 $78.37   6.579%   $83.526   $83.53   $83.55   $83.50  
  7 purchase totals = $886.99       $952.1372   $952.13   $952.15   $952.20