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 $62.55   5.123%   $65.7544   $65.75   $65.75   $65.80  
  Purchase #2 $223.84   9.162%   $244.3482   $244.35   $244.35   $244.30  
  Purchase #3 $165.84   10.367%   $183.0326   $183.03   $183.05   $183.00  
  Purchase #4 $39.95   6.857%   $42.6894   $42.69   $42.70   $42.70  
  Purchase #5 $74.85   7.109%   $80.1711   $80.17   $80.15   $80.20  
  Purchase #6 $208.97   5.130%   $219.6902   $219.69   $219.70   $219.70  
  Purchase #7 $170.41   3.377%   $176.1647   $176.16   $176.15   $176.20  
  7 purchase totals = $946.41       $1,011.8506   $1,011.84   $1,011.85   $1,011.90