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 $195.47   4.156%   $203.5937   $203.59   $203.60   $203.60  
  Purchase #2 $144.80   10.242%   $159.6304   $159.63   $159.65   $159.60  
  Purchase #3 $74.64   11.147%   $82.9601   $82.96   $82.95   $83.00  
  Purchase #4 $184.49   4.790%   $193.3271   $193.33   $193.35   $193.30  
  Purchase #5 $223.32   10.290%   $246.2996   $246.30   $246.30   $246.30  
  Purchase #6 $148.58   3.413%   $153.651   $153.65   $153.65   $153.70  
  Purchase #7 $52.46   7.224%   $56.2497   $56.25   $56.25   $56.20  
  7 purchase totals = $1,023.76       $1,095.7116   $1,095.71   $1,095.75   $1,095.70