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 $220.84   5.330%   $232.6108   $232.61   $232.60   $232.60  
  Purchase #2 $20.77   11.572%   $23.1735   $23.17   $23.15   $23.20  
  Purchase #3 $119.26   11.666%   $133.1729   $133.17   $133.15   $133.20  
  Purchase #4 $202.28   4.700%   $211.7872   $211.79   $211.80   $211.80  
  Purchase #5 $51.98   12.260%   $58.3527   $58.35   $58.35   $58.40  
  Purchase #6 $90.75   3.124%   $93.585   $93.59   $93.60   $93.60  
  Purchase #7 $120.76   9.761%   $132.5474   $132.55   $132.55   $132.50  
  7 purchase totals = $826.64       $885.2295   $885.23   $885.20   $885.30