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 $141.50   7.835%   $152.5865   $152.59   $152.60   $152.60  
  Purchase #2 $94.67   3.163%   $97.6644   $97.66   $97.65   $97.70  
  Purchase #3 $201.98   4.521%   $211.1115   $211.11   $211.10   $211.10  
  Purchase #4 $219.36   11.458%   $244.4943   $244.49   $244.50   $244.50  
  Purchase #5 $148.61   7.272%   $159.4169   $159.42   $159.40   $159.40  
  Purchase #6 $246.97   3.702%   $256.1128   $256.11   $256.10   $256.10  
  Purchase #7 $97.46   11.800%   $108.9603   $108.96   $108.95   $109.00  
  7 purchase totals = $1,150.55       $1,230.3467   $1,230.34   $1,230.30   $1,230.40