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 $148.48   8.840%   $161.6056   $161.61   $161.60   $161.60  
  Purchase #2 $244.61   12.144%   $274.3154   $274.32   $274.30   $274.30  
  Purchase #3 $8.97   12.599%   $10.1001   $10.10   $10.10   $10.10  
  Purchase #4 $167.43   12.274%   $187.9804   $187.98   $188.00   $188.00  
  Purchase #5 $113.92   4.869%   $119.4668   $119.47   $119.45   $119.50  
  Purchase #6 $148.51   12.380%   $166.8955   $166.90   $166.90   $166.90  
  Purchase #7 $133.36   11.146%   $148.2243   $148.22   $148.20   $148.20  
  7 purchase totals = $965.28       $1,068.5881   $1,068.60   $1,068.55   $1,068.60