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	$211.28	5.814%	$223.5638	$223.56	$223.55	$223.60
Purchase #2	$157.49	5.711%	$166.4843	$166.48	$166.50	$166.50
Purchase #3	$207.88	8.601%	$225.7598	$225.76	$225.75	$225.80
Purchase #4	$42.56	7.521%	$45.7609	$45.76	$45.75	$45.80
Purchase #5	$120.50	5.470%	$127.0914	$127.09	$127.10	$127.10
Purchase #6	$102.61	3.154%	$105.8463	$105.85	$105.85	$105.80
Purchase #7	$13.78	8.479%	$14.9484	$14.95	$14.95	$14.90
7 purchase totals =	$856.10		$909.4549	$909.45	$909.45	$909.50