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 $211.47   3.681%   $219.2542   $219.25   $219.25   $219.30  
  Purchase #2 $57.84   4.720%   $60.57   $60.57   $60.55   $60.60  
  Purchase #3 $67.85   12.784%   $76.5239   $76.52   $76.50   $76.50  
  Purchase #4 $216.98   12.677%   $244.4866   $244.49   $244.50   $244.50  
  Purchase #5 $204.91   10.428%   $226.278   $226.28   $226.30   $226.30  
  Purchase #6 $238.36   4.637%   $249.4128   $249.41   $249.40   $249.40  
  Purchase #7 $79.55   11.257%   $88.5049   $88.50   $88.50   $88.50  
  7 purchase totals = $1,076.96       $1,165.0304   $1,165.02   $1,165.00   $1,165.10