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	$233.76	13.242%	$264.7145	$264.71	$264.70	$264.70
Purchase #2	$166.89	13.180%	$188.8861	$188.89	$188.90	$188.90
Purchase #3	$55.76	9.693%	$61.1648	$61.16	$61.15	$61.20
Purchase #4	$151.50	12.483%	$170.4117	$170.41	$170.40	$170.40
Purchase #5	$37.30	3.404%	$38.5697	$38.57	$38.55	$38.60
Purchase #6	$208.53	12.835%	$235.2948	$235.29	$235.30	$235.30
Purchase #7	$182.27	6.300%	$193.753	$193.75	$193.75	$193.80
7 purchase totals =	$1,036.01		$1,152.7946	$1,152.78	$1,152.75	$1,152.90