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 $173.49   13.868%   $197.5496   $197.55   $197.55   $197.50  
  Purchase #2 $68.82   11.652%   $76.8389   $76.84   $76.85   $76.80  
  Purchase #3 $66.96   3.627%   $69.3886   $69.39   $69.40   $69.40  
  Purchase #4 $170.32   6.347%   $181.1302   $181.13   $181.15   $181.10  
  Purchase #5 $23.95   8.825%   $26.0636   $26.06   $26.05   $26.10  
  Purchase #6 $136.56   12.822%   $154.0697   $154.07   $154.05   $154.10  
  Purchase #7 $178.98   7.435%   $192.2872   $192.29   $192.30   $192.30  
  7 purchase totals = $819.08       $897.3278   $897.33   $897.35   $897.30