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 $45.65   13.810%   $51.9543   $51.95   $51.95   $52.00  
  Purchase #2 $248.53   11.758%   $277.7522   $277.75   $277.75   $277.80  
  Purchase #3 $55.45   11.494%   $61.8234   $61.82   $61.80   $61.80  
  Purchase #4 $219.84   3.735%   $228.051   $228.05   $228.05   $228.10  
  Purchase #5 $104.86   13.685%   $119.2101   $119.21   $119.20   $119.20  
  Purchase #6 $143.35   5.844%   $151.7274   $151.73   $151.75   $151.70  
  Purchase #7 $148.29   9.576%   $162.4903   $162.49   $162.50   $162.50  
  7 purchase totals = $965.97       $1,053.0087   $1,053.00   $1,053.00   $1,053.10