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 $126.39   5.737%   $133.641   $133.64   $133.65   $133.60  
  Purchase #2 $183.27   11.170%   $203.7413   $203.74   $203.75   $203.70  
  Purchase #3 $62.33   8.655%   $67.7247   $67.72   $67.70   $67.70  
  Purchase #4 $22.92   4.780%   $24.0156   $24.02   $24.00   $24.00  
  Purchase #5 $191.84   11.867%   $214.6057   $214.61   $214.60   $214.60  
  Purchase #6 $145.42   10.834%   $161.1748   $161.17   $161.15   $161.20  
  Purchase #7 $142.45   3.147%   $146.9329   $146.93   $146.95   $146.90  
  7 purchase totals = $874.62       $951.8360   $951.83   $951.80   $951.70