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	$207.31	4.830%	$217.3231	$217.32	$217.30	$217.30
Purchase #2	$87.64	3.757%	$90.9326	$90.93	$90.95	$90.90
Purchase #3	$237.79	13.187%	$269.1474	$269.15	$269.15	$269.10
Purchase #4	$58.61	11.627%	$65.4246	$65.42	$65.40	$65.40
Purchase #5	$195.82	13.714%	$222.6748	$222.67	$222.65	$222.70
Purchase #6	$94.35	7.212%	$101.1545	$101.15	$101.15	$101.20
Purchase #7	$159.64	3.210%	$164.7644	$164.76	$164.75	$164.80
7 purchase totals =	$1,041.16		$1,131.4214	$1,131.40	$1,131.35	$1,131.40