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 $81.66   12.677%   $92.012   $92.01   $92.00   $92.00  
  Purchase #2 $172.83   6.267%   $183.6613   $183.66   $183.65   $183.70  
  Purchase #3 $98.42   7.640%   $105.9393   $105.94   $105.95   $105.90  
  Purchase #4 $203.71   7.722%   $219.4405   $219.44   $219.45   $219.40  
  Purchase #5 $203.38   4.771%   $213.0833   $213.08   $213.10   $213.10  
  Purchase #6 $233.30   12.660%   $262.8358   $262.84   $262.85   $262.80  
  Purchase #7 $45.93   3.515%   $47.5444   $47.54   $47.55   $47.50  
  7 purchase totals = $1,039.23       $1,124.5166   $1,124.51   $1,124.55   $1,124.40