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 $42.98   3.812%   $44.6184   $44.62   $44.60   $44.60  
  Purchase #2 $94.82   12.501%   $106.6734   $106.67   $106.65   $106.70  
  Purchase #3 $182.86   7.773%   $197.0737   $197.07   $197.05   $197.10  
  Purchase #4 $211.91   4.300%   $221.0221   $221.02   $221.00   $221.00  
  Purchase #5 $184.32   4.872%   $193.3001   $193.30   $193.30   $193.30  
  Purchase #6 $187.52   6.526%   $199.7576   $199.76   $199.75   $199.80  
  Purchase #7 $161.40   6.832%   $172.4268   $172.43   $172.45   $172.40  
  7 purchase totals = $1,065.81       $1,134.8721   $1,134.87   $1,134.80   $1,134.90