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 $180.43   8.447%   $195.6709   $195.67   $195.65   $195.70  
  Purchase #2 $196.74   11.297%   $218.9657   $218.97   $218.95   $219.00  
  Purchase #3 $188.71   13.292%   $213.7933   $213.79   $213.80   $213.80  
  Purchase #4 $96.38   4.752%   $100.96   $100.96   $100.95   $101.00  
  Purchase #5 $129.98   6.169%   $137.9985   $138.00   $138.00   $138.00  
  Purchase #6 $224.82   3.437%   $232.5471   $232.55   $232.55   $232.50  
  Purchase #7 $42.41   8.469%   $46.0017   $46.00   $46.00   $46.00  
  7 purchase totals = $1,059.47       $1,145.9372   $1,145.94   $1,145.90   $1,146.00