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 $68.42   4.649%   $71.6008   $71.60   $71.60   $71.60  
  Purchase #2 $192.52   4.263%   $200.7271   $200.73   $200.75   $200.70  
  Purchase #3 $218.75   6.395%   $232.7391   $232.74   $232.75   $232.70  
  Purchase #4 $223.74   7.666%   $240.8919   $240.89   $240.90   $240.90  
  Purchase #5 $241.68   10.361%   $266.7205   $266.72   $266.70   $266.70  
  Purchase #6 $248.57   6.781%   $265.4255   $265.43   $265.45   $265.40  
  Purchase #7 $222.59   11.341%   $247.8339   $247.83   $247.85   $247.80  
  7 purchase totals = $1,416.27       $1,525.9388   $1,525.94   $1,526.00   $1,525.80