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 $86.98   9.212%   $94.9926   $94.99   $95.00   $95.00  
  Purchase #2 $196.38   7.175%   $210.4703   $210.47   $210.45   $210.50  
  Purchase #3 $204.40   3.289%   $211.1227   $211.12   $211.10   $211.10  
  Purchase #4 $143.74   10.654%   $159.0541   $159.05   $159.05   $159.10  
  Purchase #5 $249.65   7.293%   $267.857   $267.86   $267.85   $267.90  
  Purchase #6 $84.93   4.122%   $88.4308   $88.43   $88.45   $88.40  
  Purchase #7 $239.47   10.717%   $265.134   $265.13   $265.15   $265.10  
  7 purchase totals = $1,205.55       $1,297.0615   $1,297.05   $1,297.05   $1,297.10