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 $186.54   4.803%   $195.4995   $195.50   $195.50   $195.50  
  Purchase #2 $212.48   12.151%   $238.2984   $238.30   $238.30   $238.30  
  Purchase #3 $21.52   13.363%   $24.3957   $24.40   $24.40   $24.40  
  Purchase #4 $34.74   8.314%   $37.6283   $37.63   $37.65   $37.60  
  Purchase #5 $184.64   11.549%   $205.9641   $205.96   $205.95   $206.00  
  Purchase #6 $150.65   8.362%   $163.2474   $163.25   $163.25   $163.20  
  Purchase #7 $225.27   11.862%   $251.9915   $251.99   $252.00   $252.00  
  7 purchase totals = $1,015.84       $1,117.0249   $1,117.03   $1,117.05   $1,117.00