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	$159.29	10.383%	$175.8291	$175.83	$175.85	$175.80
Purchase #2	$105.91	10.432%	$116.9585	$116.96	$116.95	$117.00
Purchase #3	$147.26	3.629%	$152.6041	$152.60	$152.60	$152.60
Purchase #4	$248.68	13.697%	$282.7417	$282.74	$282.75	$282.70
Purchase #5	$118.86	7.231%	$127.4548	$127.45	$127.45	$127.50
Purchase #6	$41.50	10.403%	$45.8172	$45.82	$45.80	$45.80
Purchase #7	$56.55	5.469%	$59.6427	$59.64	$59.65	$59.60
7 purchase totals =	$878.05		$961.0481	$961.04	$961.05	$961.00