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	$233.78	13.321%	$264.9218	$264.92	$264.90	$264.90
Purchase #2	$146.58	8.190%	$158.5849	$158.58	$158.60	$158.60
Purchase #3	$50.75	6.154%	$53.8732	$53.87	$53.85	$53.90
Purchase #4	$106.78	4.680%	$111.7773	$111.78	$111.80	$111.80
Purchase #5	$91.60	9.131%	$99.964	$99.96	$99.95	$100.00
Purchase #6	$10.96	12.488%	$12.3287	$12.33	$12.35	$12.30
Purchase #7	$125.64	4.695%	$131.5388	$131.54	$131.55	$131.50
7 purchase totals =	$766.09		$832.9887	$832.98	$833.00	$833.00