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	$54.57	10.500%	$60.2999	$60.30	$60.30	$60.30
Purchase #2	$90.72	4.276%	$94.5992	$94.60	$94.60	$94.60
Purchase #3	$211.30	5.697%	$223.3378	$223.34	$223.35	$223.30
Purchase #4	$58.61	5.470%	$61.816	$61.82	$61.80	$61.80
Purchase #5	$175.78	10.429%	$194.1121	$194.11	$194.10	$194.10
Purchase #6	$18.34	11.233%	$20.4001	$20.40	$20.40	$20.40
Purchase #7	$248.85	3.683%	$258.0151	$258.02	$258.00	$258.00
7 purchase totals =	$858.17		$912.5802	$912.59	$912.55	$912.50