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 $163.27   13.119%   $184.6894   $184.69   $184.70   $184.70  
  Purchase #2 $195.96   12.106%   $219.6829   $219.68   $219.70   $219.70  
  Purchase #3 $8.45   12.437%   $9.5009   $9.50   $9.50   $9.50  
  Purchase #4 $141.27   7.820%   $152.3173   $152.32   $152.30   $152.30  
  Purchase #5 $118.72   9.668%   $130.1978   $130.20   $130.20   $130.20  
  Purchase #6 $113.88   3.477%   $117.8396   $117.84   $117.85   $117.80  
  Purchase #7 $75.51   6.153%   $80.1561   $80.16   $80.15   $80.20  
  7 purchase totals = $817.06       $894.3840   $894.39   $894.40   $894.40