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 $97.26   11.528%   $108.4721   $108.47   $108.45   $108.50  
  Purchase #2 $27.98   5.769%   $29.5942   $29.59   $29.60   $29.60  
  Purchase #3 $115.79   3.160%   $119.449   $119.45   $119.45   $119.40  
  Purchase #4 $40.29   13.292%   $45.6453   $45.65   $45.65   $45.60  
  Purchase #5 $243.49   12.243%   $273.3005   $273.30   $273.30   $273.30  
  Purchase #6 $201.99   3.629%   $209.3202   $209.32   $209.30   $209.30  
  Purchase #7 $229.51   7.541%   $246.8173   $246.82   $246.80   $246.80  
  7 purchase totals = $956.31       $1,032.5986   $1,032.60   $1,032.55   $1,032.50