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 $168.74   7.700%   $181.733   $181.73   $181.75   $181.70  
  Purchase #2 $233.88   4.631%   $244.711   $244.71   $244.70   $244.70  
  Purchase #3 $83.51   7.270%   $89.5812   $89.58   $89.60   $89.60  
  Purchase #4 $222.79   8.779%   $242.3487   $242.35   $242.35   $242.30  
  Purchase #5 $93.70   9.844%   $102.9238   $102.92   $102.90   $102.90  
  Purchase #6 $170.51   8.842%   $185.5865   $185.59   $185.60   $185.60  
  Purchase #7 $184.76   10.342%   $203.8679   $203.87   $203.85   $203.90  
  7 purchase totals = $1,157.89       $1,250.7521   $1,250.75   $1,250.75   $1,250.70