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 $204.64   3.484%   $211.7697   $211.77   $211.75   $211.80  
  Purchase #2 $250.41   7.402%   $268.9453   $268.95   $268.95   $268.90  
  Purchase #3 $22.50   11.679%   $25.1278   $25.13   $25.15   $25.10  
  Purchase #4 $216.54   9.565%   $237.2521   $237.25   $237.25   $237.30  
  Purchase #5 $155.85   9.647%   $170.8848   $170.88   $170.90   $170.90  
  Purchase #6 $188.39   12.297%   $211.5563   $211.56   $211.55   $211.60  
  Purchase #7 $41.75   3.250%   $43.1069   $43.11   $43.10   $43.10  
  7 purchase totals = $1,080.08       $1,168.6429   $1,168.65   $1,168.65   $1,168.70