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	$137.63	6.552%	$146.6475	$146.65	$146.65	$146.60
Purchase #2	$123.50	8.733%	$134.2853	$134.29	$134.30	$134.30
Purchase #3	$149.36	6.183%	$158.5949	$158.59	$158.60	$158.60
Purchase #4	$64.99	9.292%	$71.0289	$71.03	$71.05	$71.00
Purchase #5	$97.50	7.267%	$104.5853	$104.59	$104.60	$104.60
Purchase #6	$248.56	13.617%	$282.4064	$282.41	$282.40	$282.40
Purchase #7	$150.73	9.673%	$165.3101	$165.31	$165.30	$165.30
7 purchase totals =	$972.27		$1,062.8584	$1,062.87	$1,062.90	$1,062.80