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	$71.63	9.432%	$78.3861	$78.39	$78.40	$78.40
Purchase #2	$224.42	11.188%	$249.5281	$249.53	$249.55	$249.50
Purchase #3	$231.66	9.722%	$254.182	$254.18	$254.20	$254.20
Purchase #4	$196.38	8.142%	$212.3693	$212.37	$212.35	$212.40
Purchase #5	$100.35	4.774%	$105.1407	$105.14	$105.15	$105.10
Purchase #6	$52.97	8.698%	$57.5773	$57.58	$57.60	$57.60
Purchase #7	$189.48	11.719%	$211.6852	$211.69	$211.70	$211.70
7 purchase totals =	$1,066.89		$1,168.8687	$1,168.88	$1,168.95	$1,168.90