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 $187.33   6.209%   $198.9613   $198.96   $198.95   $199.00  
  Purchase #2 $69.84   7.321%   $74.953   $74.95   $74.95   $75.00  
  Purchase #3 $188.38   13.281%   $213.3987   $213.40   $213.40   $213.40  
  Purchase #4 $187.76   8.624%   $203.9524   $203.95   $203.95   $204.00  
  Purchase #5 $177.45   13.364%   $201.1644   $201.16   $201.15   $201.20  
  Purchase #6 $51.98   13.734%   $59.1189   $59.12   $59.10   $59.10  
  Purchase #7 $199.27   5.623%   $210.475   $210.48   $210.50   $210.50  
  7 purchase totals = $1,062.01       $1,162.0237   $1,162.02   $1,162.00   $1,162.20