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 $83.64   12.374%   $93.9896   $93.99   $94.00   $94.00  
  Purchase #2 $172.29   5.250%   $181.3352   $181.34   $181.35   $181.30  
  Purchase #3 $231.61   5.237%   $243.7394   $243.74   $243.75   $243.70  
  Purchase #4 $99.46   11.473%   $110.871   $110.87   $110.85   $110.90  
  Purchase #5 $125.50   9.329%   $137.2079   $137.21   $137.20   $137.20  
  Purchase #6 $203.25   10.751%   $225.1014   $225.10   $225.10   $225.10  
  Purchase #7 $65.28   7.665%   $70.2837   $70.28   $70.30   $70.30  
  7 purchase totals = $981.03       $1,062.5282   $1,062.53   $1,062.55   $1,062.50