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	$58.51	5.829%	$61.9205	$61.92	$61.90	$61.90
Purchase #2	$117.65	8.145%	$127.2326	$127.23	$127.25	$127.20
Purchase #3	$165.60	13.160%	$187.393	$187.39	$187.40	$187.40
Purchase #4	$151.91	11.763%	$169.7792	$169.78	$169.80	$169.80
Purchase #5	$249.63	8.335%	$270.4367	$270.44	$270.45	$270.40
Purchase #6	$80.51	11.181%	$89.5118	$89.51	$89.50	$89.50
Purchase #7	$85.26	13.316%	$96.6132	$96.61	$96.60	$96.60
7 purchase totals =	$909.07		$1,002.8870	$1,002.88	$1,002.90	$1,002.80