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	$112.54	12.850%	$127.0014	$127.00	$127.00	$127.00
Purchase #2	$183.65	8.628%	$199.4953	$199.50	$199.50	$199.50
Purchase #3	$53.63	12.459%	$60.3118	$60.31	$60.30	$60.30
Purchase #4	$68.51	4.400%	$71.5244	$71.52	$71.50	$71.50
Purchase #5	$37.40	13.846%	$42.5784	$42.58	$42.60	$42.60
Purchase #6	$17.40	6.550%	$18.5397	$18.54	$18.55	$18.50
Purchase #7	$147.96	7.366%	$158.8587	$158.86	$158.85	$158.90
7 purchase totals =	$621.09		$678.3097	$678.31	$678.30	$678.30