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 $79.36   11.668%   $88.6197   $88.62   $88.60   $88.60  
  Purchase #2 $194.84   9.803%   $213.9402   $213.94   $213.95   $213.90  
  Purchase #3 $22.90   5.323%   $24.119   $24.12   $24.10   $24.10  
  Purchase #4 $247.29   6.440%   $263.2155   $263.22   $263.20   $263.20  
  Purchase #5 $151.94   10.119%   $167.3148   $167.31   $167.30   $167.30  
  Purchase #6 $217.97   8.587%   $236.6871   $236.69   $236.70   $236.70  
  Purchase #7 $192.91   4.417%   $201.4308   $201.43   $201.45   $201.40  
  7 purchase totals = $1,107.21       $1,195.3271   $1,195.33   $1,195.30   $1,195.20