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 $91.26   4.311%   $95.1942   $95.19   $95.20   $95.20  
  Purchase #2 $214.93   3.452%   $222.3494   $222.35   $222.35   $222.30  
  Purchase #3 $153.98   13.430%   $174.6595   $174.66   $174.65   $174.70  
  Purchase #4 $216.65   8.521%   $235.1107   $235.11   $235.10   $235.10  
  Purchase #5 $111.56   11.121%   $123.9666   $123.97   $123.95   $124.00  
  Purchase #6 $182.72   10.661%   $202.1998   $202.20   $202.20   $202.20  
  Purchase #7 $109.84   11.390%   $122.3508   $122.35   $122.35   $122.40  
  7 purchase totals = $1,080.94       $1,175.8310   $1,175.83   $1,175.80   $1,175.90