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	$14.75	7.380%	$15.8386	$15.84	$15.85	$15.80
Purchase #2	$87.35	12.344%	$98.1325	$98.13	$98.15	$98.10
Purchase #3	$95.85	5.236%	$100.8687	$100.87	$100.85	$100.90
Purchase #4	$210.27	5.845%	$222.5603	$222.56	$222.55	$222.60
Purchase #5	$236.64	13.814%	$269.3294	$269.33	$269.35	$269.30
Purchase #6	$76.47	12.180%	$85.784	$85.78	$85.80	$85.80
Purchase #7	$147.89	11.687%	$165.1739	$165.17	$165.15	$165.20
7 purchase totals =	$869.22		$957.6874	$957.68	$957.70	$957.70