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 $85.65   11.247%   $95.2831   $95.28   $95.30   $95.30  
  Purchase #2 $93.86   6.667%   $100.1176   $100.12   $100.10   $100.10  
  Purchase #3 $137.27   6.321%   $145.9468   $145.95   $145.95   $145.90  
  Purchase #4 $199.42   3.207%   $205.8154   $205.82   $205.80   $205.80  
  Purchase #5 $232.80   6.545%   $248.0368   $248.04   $248.05   $248.00  
  Purchase #6 $246.92   6.629%   $263.2883   $263.29   $263.30   $263.30  
  Purchase #7 $179.83   12.478%   $202.2692   $202.27   $202.25   $202.30  
  7 purchase totals = $1,175.75       $1,260.7572   $1,260.77   $1,260.75   $1,260.70