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	$71.34	10.335%	$78.713	$78.71	$78.70	$78.70
Purchase #2	$67.76	12.661%	$76.3391	$76.34	$76.35	$76.30
Purchase #3	$154.65	7.618%	$166.4312	$166.43	$166.45	$166.40
Purchase #4	$10.86	4.573%	$11.3566	$11.36	$11.35	$11.40
Purchase #5	$222.94	3.375%	$230.4642	$230.46	$230.45	$230.50
Purchase #6	$96.78	8.694%	$105.1941	$105.19	$105.20	$105.20
Purchase #7	$60.69	3.841%	$63.0211	$63.02	$63.00	$63.00
7 purchase totals =	$685.02		$731.5193	$731.51	$731.50	$731.50