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	$117.36	11.156%	$130.4527	$130.45	$130.45	$130.50
Purchase #2	$196.65	8.580%	$213.5226	$213.52	$213.50	$213.50
Purchase #3	$210.46	5.610%	$222.2668	$222.27	$222.25	$222.30
Purchase #4	$146.86	8.237%	$158.9569	$158.96	$158.95	$159.00
Purchase #5	$99.56	12.657%	$112.1613	$112.16	$112.15	$112.20
Purchase #6	$11.78	3.317%	$12.1707	$12.17	$12.15	$12.20
Purchase #7	$224.39	7.452%	$241.1115	$241.11	$241.10	$241.10
7 purchase totals =	$1,007.06		$1,090.6425	$1,090.64	$1,090.55	$1,090.80