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 $65.92   10.673%   $72.9556   $72.96   $72.95   $73.00  
  Purchase #2 $201.60   8.145%   $218.0203   $218.02   $218.00   $218.00  
  Purchase #3 $101.57   10.789%   $112.5284   $112.53   $112.55   $112.50  
  Purchase #4 $238.70   9.117%   $260.4623   $260.46   $260.45   $260.50  
  Purchase #5 $62.48   12.341%   $70.1907   $70.19   $70.20   $70.20  
  Purchase #6 $132.88   11.341%   $147.9499   $147.95   $147.95   $147.90  
  Purchase #7 $170.58   9.416%   $186.6418   $186.64   $186.65   $186.60  
  7 purchase totals = $973.73       $1,068.7490   $1,068.75   $1,068.75   $1,068.70