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	$57.38	6.839%	$61.3042	$61.30	$61.30	$61.30
Purchase #2	$21.91	10.827%	$24.2822	$24.28	$24.30	$24.30
Purchase #3	$82.79	10.629%	$91.5897	$91.59	$91.60	$91.60
Purchase #4	$61.29	7.336%	$65.7862	$65.79	$65.80	$65.80
Purchase #5	$53.82	8.310%	$58.2924	$58.29	$58.30	$58.30
Purchase #6	$103.41	7.698%	$111.3705	$111.37	$111.35	$111.40
Purchase #7	$35.76	13.620%	$40.6305	$40.63	$40.65	$40.60
7 purchase totals =	$416.36		$453.2557	$453.25	$453.30	$453.30