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	$178.30	7.525%	$191.7171	$191.72	$191.70	$191.70
Purchase #2	$181.32	7.833%	$195.5228	$195.52	$195.50	$195.50
Purchase #3	$15.77	11.442%	$17.5744	$17.57	$17.55	$17.60
Purchase #4	$74.45	5.476%	$78.5269	$78.53	$78.55	$78.50
Purchase #5	$159.76	6.104%	$169.5118	$169.51	$169.50	$169.50
Purchase #6	$131.70	13.804%	$149.8799	$149.88	$149.90	$149.90
Purchase #7	$250.41	5.499%	$264.18	$264.18	$264.20	$264.20
7 purchase totals =	$991.71		$1,066.9129	$1,066.91	$1,066.90	$1,066.90