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	$235.69	11.407%	$262.5752	$262.58	$262.60	$262.60
Purchase #2	$204.98	5.224%	$215.6882	$215.69	$215.70	$215.70
Purchase #3	$55.95	9.588%	$61.3145	$61.31	$61.30	$61.30
Purchase #4	$248.58	8.674%	$270.1418	$270.14	$270.15	$270.10
Purchase #5	$126.32	5.221%	$132.9152	$132.92	$132.90	$132.90
Purchase #6	$95.37	6.362%	$101.4374	$101.44	$101.45	$101.40
Purchase #7	$226.72	13.207%	$256.6629	$256.66	$256.65	$256.70
7 purchase totals =	$1,193.61		$1,300.7352	$1,300.74	$1,300.75	$1,300.70