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	$224.27	6.629%	$239.1369	$239.14	$239.15	$239.10
Purchase #2	$11.87	13.515%	$13.4742	$13.47	$13.45	$13.50
Purchase #3	$54.51	9.589%	$59.737	$59.74	$59.75	$59.70
Purchase #4	$45.32	11.502%	$50.5327	$50.53	$50.55	$50.50
Purchase #5	$190.56	13.659%	$216.5886	$216.59	$216.60	$216.60
Purchase #6	$214.66	11.605%	$239.5713	$239.57	$239.55	$239.60
Purchase #7	$159.26	3.789%	$165.2944	$165.29	$165.30	$165.30
7 purchase totals =	$900.45		$984.3351	$984.33	$984.35	$984.30