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	$243.89	3.757%	$253.0529	$253.05	$253.05	$253.10
Purchase #2	$53.65	10.571%	$59.3213	$59.32	$59.30	$59.30
Purchase #3	$37.48	12.703%	$42.2411	$42.24	$42.25	$42.20
Purchase #4	$126.66	10.747%	$140.2722	$140.27	$140.25	$140.30
Purchase #5	$111.69	4.367%	$116.5675	$116.57	$116.55	$116.60
Purchase #6	$5.33	4.493%	$5.5695	$5.57	$5.55	$5.60
Purchase #7	$14.47	3.467%	$14.9717	$14.97	$14.95	$15.00
7 purchase totals =	$593.17		$631.9962	$631.99	$631.90	$632.10