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 $68.87   9.670%   $75.5297   $75.53   $75.55   $75.50  
  Purchase #2 $130.48   11.663%   $145.6979   $145.70   $145.70   $145.70  
  Purchase #3 $238.87   3.602%   $247.4741   $247.47   $247.45   $247.50  
  Purchase #4 $55.64   6.689%   $59.3618   $59.36   $59.35   $59.40  
  Purchase #5 $246.64   8.723%   $268.1544   $268.15   $268.15   $268.20  
  Purchase #6 $64.39   7.649%   $69.3152   $69.32   $69.30   $69.30  
  Purchase #7 $216.62   9.165%   $236.4732   $236.47   $236.45   $236.50  
  7 purchase totals = $1,021.51       $1,102.0063   $1,102.00   $1,101.95   $1,102.10