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 $208.93   4.810%   $218.9795   $218.98   $219.00   $219.00  
  Purchase #2 $192.80   6.577%   $205.4805   $205.48   $205.50   $205.50  
  Purchase #3 $27.30   11.639%   $30.4774   $30.48   $30.50   $30.50  
  Purchase #4 $250.84   5.182%   $263.8385   $263.84   $263.85   $263.80  
  Purchase #5 $44.64   4.390%   $46.5997   $46.60   $46.60   $46.60  
  Purchase #6 $192.43   6.467%   $204.8744   $204.87   $204.85   $204.90  
  Purchase #7 $167.59   8.426%   $181.7111   $181.71   $181.70   $181.70  
  7 purchase totals = $1,084.53       $1,151.9611   $1,151.96   $1,152.00   $1,152.00