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 $41.65   5.150%   $43.795   $43.80   $43.80   $43.80  
  Purchase #2 $220.89   5.145%   $232.2548   $232.25   $232.25   $232.30  
  Purchase #3 $183.50   6.679%   $195.756   $195.76   $195.75   $195.80  
  Purchase #4 $81.67   4.524%   $85.3648   $85.36   $85.35   $85.40  
  Purchase #5 $203.35   5.172%   $213.8673   $213.87   $213.85   $213.90  
  Purchase #6 $173.33   12.666%   $195.284   $195.28   $195.30   $195.30  
  Purchase #7 $165.32   11.738%   $184.7253   $184.73   $184.75   $184.70  
  7 purchase totals = $1,069.71       $1,151.0472   $1,151.05   $1,151.05   $1,151.20