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	$147.39	4.125%	$153.4698	$153.47	$153.45	$153.50
Purchase #2	$73.68	6.725%	$78.635	$78.64	$78.65	$78.60
Purchase #3	$107.60	9.261%	$117.5648	$117.56	$117.55	$117.60
Purchase #4	$44.64	13.263%	$50.5606	$50.56	$50.55	$50.60
Purchase #5	$85.73	4.519%	$89.6041	$89.60	$89.60	$89.60
Purchase #6	$206.54	11.649%	$230.5998	$230.60	$230.60	$230.60
Purchase #7	$243.93	12.256%	$273.8261	$273.83	$273.85	$273.80
7 purchase totals =	$909.51		$994.2602	$994.26	$994.25	$994.30