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	$62.34	6.266%	$66.2462	$66.25	$66.25	$66.20
Purchase #2	$141.86	3.834%	$147.2989	$147.30	$147.30	$147.30
Purchase #3	$101.75	12.688%	$114.66	$114.66	$114.65	$114.70
Purchase #4	$200.55	10.340%	$221.2869	$221.29	$221.30	$221.30
Purchase #5	$109.39	8.259%	$118.4245	$118.42	$118.40	$118.40
Purchase #6	$210.85	10.789%	$233.5986	$233.60	$233.60	$233.60
Purchase #7	$241.58	12.123%	$270.8667	$270.87	$270.85	$270.90
7 purchase totals =	$1,068.32		$1,172.3818	$1,172.39	$1,172.35	$1,172.40