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 $147.95   9.851%   $162.5246   $162.52   $162.50   $162.50  
  Purchase #2 $214.47   4.530%   $224.1855   $224.19   $224.20   $224.20  
  Purchase #3 $26.73   7.523%   $28.7409   $28.74   $28.75   $28.70  
  Purchase #4 $95.42   3.560%   $98.817   $98.82   $98.80   $98.80  
  Purchase #5 $72.97   5.249%   $76.8002   $76.80   $76.80   $76.80  
  Purchase #6 $246.29   11.386%   $274.3326   $274.33   $274.35   $274.30  
  Purchase #7 $225.85   6.270%   $240.0108   $240.01   $240.00   $240.00  
  7 purchase totals = $1,029.68       $1,105.4116   $1,105.41   $1,105.40   $1,105.30