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	$86.41	3.538%	$89.4672	$89.47	$89.45	$89.50
Purchase #2	$117.33	8.265%	$127.0273	$127.03	$127.05	$127.00
Purchase #3	$148.54	12.234%	$166.7124	$166.71	$166.70	$166.70
Purchase #4	$12.84	13.550%	$14.5798	$14.58	$14.60	$14.60
Purchase #5	$91.73	6.363%	$97.5668	$97.57	$97.55	$97.60
Purchase #6	$158.78	12.749%	$179.0229	$179.02	$179.00	$179.00
Purchase #7	$38.98	12.172%	$43.7246	$43.72	$43.70	$43.70
7 purchase totals =	$654.61		$718.1010	$718.10	$718.05	$718.10