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 $88.49   6.868%   $94.5675   $94.57   $94.55   $94.60  
  Purchase #2 $194.47   4.206%   $202.6494   $202.65   $202.65   $202.60  
  Purchase #3 $75.31   6.692%   $80.3497   $80.35   $80.35   $80.30  
  Purchase #4 $209.46   8.582%   $227.4359   $227.44   $227.45   $227.40  
  Purchase #5 $54.66   13.573%   $62.079   $62.08   $62.10   $62.10  
  Purchase #6 $249.75   5.719%   $264.0332   $264.03   $264.05   $264.00  
  Purchase #7 $213.75   7.663%   $230.1297   $230.13   $230.15   $230.10  
  7 purchase totals = $1,085.89       $1,161.2444   $1,161.25   $1,161.30   $1,161.10