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	$168.68	13.441%	$191.3523	$191.35	$191.35	$191.40
Purchase #2	$229.71	10.870%	$254.6795	$254.68	$254.70	$254.70
Purchase #3	$223.52	10.873%	$247.8233	$247.82	$247.80	$247.80
Purchase #4	$134.87	13.189%	$152.658	$152.66	$152.65	$152.70
Purchase #5	$112.64	9.649%	$123.5086	$123.51	$123.50	$123.50
Purchase #6	$51.78	3.741%	$53.7171	$53.72	$53.70	$53.70
Purchase #7	$173.72	9.243%	$189.7769	$189.78	$189.80	$189.80
7 purchase totals =	$1,094.92		$1,213.5157	$1,213.52	$1,213.50	$1,213.60