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 $184.68   5.592%   $195.0073   $195.01   $195.00   $195.00  
  Purchase #2 $123.95   8.635%   $134.6531   $134.65   $134.65   $134.70  
  Purchase #3 $59.32   9.385%   $64.8872   $64.89   $64.90   $64.90  
  Purchase #4 $86.63   7.486%   $93.1151   $93.12   $93.10   $93.10  
  Purchase #5 $198.30   10.732%   $219.5816   $219.58   $219.60   $219.60  
  Purchase #6 $41.86   9.216%   $45.7178   $45.72   $45.70   $45.70  
  Purchase #7 $7.80   6.696%   $8.3223   $8.32   $8.30   $8.30  
  7 purchase totals = $702.54       $761.2844   $761.29   $761.25   $761.30