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	$123.88	13.370%	$140.4428	$140.44	$140.45	$140.40
Purchase #2	$151.59	5.753%	$160.311	$160.31	$160.30	$160.30
Purchase #3	$250.32	13.823%	$284.9217	$284.92	$284.90	$284.90
Purchase #4	$235.68	8.586%	$255.9155	$255.92	$255.90	$255.90
Purchase #5	$37.25	11.162%	$41.4078	$41.41	$41.40	$41.40
Purchase #6	$85.92	13.140%	$97.2099	$97.21	$97.20	$97.20
Purchase #7	$87.90	4.591%	$91.9355	$91.94	$91.95	$91.90
7 purchase totals =	$972.54		$1,072.1442	$1,072.15	$1,072.10	$1,072.00