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 $192.73   5.819%   $203.945   $203.95   $203.95   $203.90  
  Purchase #2 $65.48   7.555%   $70.427   $70.43   $70.45   $70.40  
  Purchase #3 $207.98   5.633%   $219.6955   $219.70   $219.70   $219.70  
  Purchase #4 $159.31   12.502%   $179.2269   $179.23   $179.25   $179.20  
  Purchase #5 $240.89   3.154%   $248.4877   $248.49   $248.50   $248.50  
  Purchase #6 $137.61   10.596%   $152.1912   $152.19   $152.20   $152.20  
  Purchase #7 $49.39   7.106%   $52.8997   $52.90   $52.90   $52.90  
  7 purchase totals = $1,053.39       $1,126.8730   $1,126.89   $1,126.95   $1,126.80