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 $8.92   9.398%   $9.7583   $9.76   $9.75   $9.80  
  Purchase #2 $179.62   12.617%   $202.2827   $202.28   $202.30   $202.30  
  Purchase #3 $51.55   8.438%   $55.8998   $55.90   $55.90   $55.90  
  Purchase #4 $166.65   9.170%   $181.9318   $181.93   $181.95   $181.90  
  Purchase #5 $248.40   10.361%   $274.1367   $274.14   $274.15   $274.10  
  Purchase #6 $227.74   12.415%   $256.0139   $256.01   $256.00   $256.00  
  Purchase #7 $165.87   4.599%   $173.4984   $173.50   $173.50   $173.50  
  7 purchase totals = $1,048.75       $1,153.5216   $1,153.52   $1,153.55   $1,153.50