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 $87.32   8.523%   $94.7623   $94.76   $94.75   $94.80  
  Purchase #2 $116.50   9.826%   $127.9473   $127.95   $127.95   $127.90  
  Purchase #3 $145.76   5.566%   $153.873   $153.87   $153.85   $153.90  
  Purchase #4 $123.93   3.673%   $128.4819   $128.48   $128.50   $128.50  
  Purchase #5 $194.91   6.118%   $206.8346   $206.83   $206.85   $206.80  
  Purchase #6 $188.70   7.530%   $202.9091   $202.91   $202.90   $202.90  
  Purchase #7 $99.71   3.151%   $102.8519   $102.85   $102.85   $102.90  
  7 purchase totals = $956.83       $1,017.6601   $1,017.65   $1,017.65   $1,017.70