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	$82.86	9.413%	$90.6596	$90.66	$90.65	$90.70
Purchase #2	$171.50	11.726%	$191.6101	$191.61	$191.60	$191.60
Purchase #3	$6.28	4.571%	$6.5671	$6.57	$6.55	$6.60
Purchase #4	$117.29	5.826%	$124.1233	$124.12	$124.10	$124.10
Purchase #5	$92.81	4.128%	$96.6412	$96.64	$96.65	$96.60
Purchase #6	$189.72	11.389%	$211.3272	$211.33	$211.35	$211.30
Purchase #7	$15.40	7.613%	$16.5724	$16.57	$16.55	$16.60
7 purchase totals =	$675.86		$737.5009	$737.50	$737.45	$737.50