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	$52.74	6.681%	$56.2636	$56.26	$56.25	$56.30
Purchase #2	$89.67	10.436%	$99.028	$99.03	$99.05	$99.00
Purchase #3	$138.64	5.765%	$146.6326	$146.63	$146.65	$146.60
Purchase #4	$148.91	6.209%	$158.1558	$158.16	$158.15	$158.20
Purchase #5	$247.54	13.766%	$281.6164	$281.62	$281.60	$281.60
Purchase #6	$132.80	7.415%	$142.6471	$142.65	$142.65	$142.60
Purchase #7	$166.59	12.380%	$187.2138	$187.21	$187.20	$187.20
7 purchase totals =	$976.89		$1,071.5573	$1,071.56	$1,071.55	$1,071.50