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 $50.98   7.397%   $54.751   $54.75   $54.75   $54.80  
  Purchase #2 $182.37   5.387%   $192.1943   $192.19   $192.20   $192.20  
  Purchase #3 $166.63   10.640%   $184.3594   $184.36   $184.35   $184.40  
  Purchase #4 $200.67   9.473%   $219.6795   $219.68   $219.70   $219.70  
  Purchase #5 $216.94   8.692%   $235.7964   $235.80   $235.80   $235.80  
  Purchase #6 $164.90   7.396%   $177.096   $177.10   $177.10   $177.10  
  Purchase #7 $152.32   5.122%   $160.1218   $160.12   $160.10   $160.10  
  7 purchase totals = $1,134.81       $1,223.9984   $1,224.00   $1,224.00   $1,224.10