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	$58.79	4.676%	$61.539	$61.54	$61.55	$61.50
Purchase #2	$43.88	7.419%	$47.1355	$47.14	$47.15	$47.10
Purchase #3	$67.73	6.440%	$72.0918	$72.09	$72.10	$72.10
Purchase #4	$108.76	10.572%	$120.2581	$120.26	$120.25	$120.30
Purchase #5	$184.59	3.590%	$191.2168	$191.22	$191.20	$191.20
Purchase #6	$230.60	13.150%	$260.9239	$260.92	$260.90	$260.90
Purchase #7	$95.40	11.733%	$106.5933	$106.59	$106.60	$106.60
7 purchase totals =	$789.75		$859.7584	$859.76	$859.75	$859.70