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	$65.90	7.810%	$71.0468	$71.05	$71.05	$71.00
Purchase #2	$92.91	8.560%	$100.8631	$100.86	$100.85	$100.90
Purchase #3	$89.60	5.217%	$94.2744	$94.27	$94.25	$94.30
Purchase #4	$143.95	7.472%	$154.7059	$154.71	$154.70	$154.70
Purchase #5	$101.90	10.844%	$112.95	$112.95	$112.95	$113.00
Purchase #6	$10.39	4.719%	$10.8803	$10.88	$10.90	$10.90
Purchase #7	$232.72	5.122%	$244.6399	$244.64	$244.65	$244.60
7 purchase totals =	$737.37		$789.3604	$789.36	$789.35	$789.40