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	$151.60	9.297%	$165.6943	$165.69	$165.70	$165.70
Purchase #2	$124.96	10.370%	$137.9184	$137.92	$137.90	$137.90
Purchase #3	$168.65	6.252%	$179.194	$179.19	$179.20	$179.20
Purchase #4	$248.81	8.228%	$269.2821	$269.28	$269.30	$269.30
Purchase #5	$225.63	11.169%	$250.8306	$250.83	$250.85	$250.80
Purchase #6	$18.65	8.850%	$20.3005	$20.30	$20.30	$20.30
Purchase #7	$150.60	3.104%	$155.2746	$155.27	$155.25	$155.30
7 purchase totals =	$1,088.90		$1,178.4945	$1,178.48	$1,178.50	$1,178.50