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 $195.87   3.463%   $202.653   $202.65   $202.65   $202.70  
  Purchase #2 $116.42   8.764%   $126.623   $126.62   $126.60   $126.60  
  Purchase #3 $54.30   6.534%   $57.848   $57.85   $57.85   $57.80  
  Purchase #4 $163.52   7.591%   $175.9328   $175.93   $175.95   $175.90  
  Purchase #5 $218.44   11.342%   $243.2155   $243.22   $243.20   $243.20  
  Purchase #6 $117.75   5.579%   $124.3193   $124.32   $124.30   $124.30  
  Purchase #7 $230.64   12.667%   $259.8552   $259.86   $259.85   $259.90  
  7 purchase totals = $1,096.94       $1,190.4468   $1,190.45   $1,190.40   $1,190.40