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	$154.38	7.234%	$165.5478	$165.55	$165.55	$165.50
Purchase #2	$209.65	6.131%	$222.5036	$222.50	$222.50	$222.50
Purchase #3	$25.63	13.568%	$29.1075	$29.11	$29.10	$29.10
Purchase #4	$93.27	12.302%	$104.7441	$104.74	$104.75	$104.70
Purchase #5	$239.57	9.845%	$263.1557	$263.16	$263.15	$263.20
Purchase #6	$59.61	3.181%	$61.5062	$61.51	$61.50	$61.50
Purchase #7	$89.85	6.770%	$95.9328	$95.93	$95.95	$95.90
7 purchase totals =	$871.96		$942.4977	$942.50	$942.50	$942.40