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	$105.89	9.157%	$115.5863	$115.59	$115.60	$115.60
Purchase #2	$159.75	5.666%	$168.8014	$168.80	$168.80	$168.80
Purchase #3	$42.78	11.794%	$47.8255	$47.83	$47.85	$47.80
Purchase #4	$63.46	3.306%	$65.558	$65.56	$65.55	$65.60
Purchase #5	$191.32	9.605%	$209.6963	$209.70	$209.70	$209.70
Purchase #6	$168.57	10.646%	$186.516	$186.52	$186.50	$186.50
Purchase #7	$243.91	12.542%	$274.5012	$274.50	$274.50	$274.50
7 purchase totals =	$975.68		$1,068.4847	$1,068.50	$1,068.50	$1,068.50