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	$82.86	11.563%	$92.4411	$92.44	$92.45	$92.40
Purchase #2	$55.51	10.815%	$61.5134	$61.51	$61.50	$61.50
Purchase #3	$40.92	12.210%	$45.9163	$45.92	$45.90	$45.90
Purchase #4	$233.95	10.535%	$258.5966	$258.60	$258.60	$258.60
Purchase #5	$46.68	7.146%	$50.0158	$50.02	$50.00	$50.00
Purchase #6	$6.99	13.314%	$7.9206	$7.92	$7.90	$7.90
Purchase #7	$206.79	5.359%	$217.8719	$217.87	$217.85	$217.90
7 purchase totals =	$673.70		$734.2757	$734.28	$734.20	$734.20