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 $223.36   9.463%   $244.4966   $244.50   $244.50   $244.50  
  Purchase #2 $137.87   8.566%   $149.6799   $149.68   $149.70   $149.70  
  Purchase #3 $152.94   11.372%   $170.3323   $170.33   $170.35   $170.30  
  Purchase #4 $115.45   7.573%   $124.193   $124.19   $124.20   $124.20  
  Purchase #5 $11.33   13.815%   $12.8952   $12.90   $12.90   $12.90  
  Purchase #6 $211.81   3.659%   $219.5601   $219.56   $219.55   $219.60  
  Purchase #7 $153.44   13.296%   $173.8414   $173.84   $173.85   $173.80  
  7 purchase totals = $1,006.20       $1,094.9985   $1,095.00   $1,095.05   $1,095.00