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	$108.45	10.102%	$119.4056	$119.41	$119.40	$119.40
Purchase #2	$66.72	13.850%	$75.9607	$75.96	$75.95	$76.00
Purchase #3	$58.31	13.260%	$66.0419	$66.04	$66.05	$66.00
Purchase #4	$33.65	10.808%	$37.2869	$37.29	$37.30	$37.30
Purchase #5	$82.26	9.343%	$89.9456	$89.95	$89.95	$89.90
Purchase #6	$166.50	4.748%	$174.4054	$174.41	$174.40	$174.40
Purchase #7	$48.26	4.827%	$50.5895	$50.59	$50.60	$50.60
7 purchase totals =	$564.15		$613.6356	$613.65	$613.65	$613.60