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	$156.36	5.567%	$165.0646	$165.06	$165.05	$165.10
Purchase #2	$10.95	13.861%	$12.4678	$12.47	$12.45	$12.50
Purchase #3	$24.46	11.447%	$27.2599	$27.26	$27.25	$27.30
Purchase #4	$26.62	8.427%	$28.8633	$28.86	$28.85	$28.90
Purchase #5	$47.66	13.504%	$54.096	$54.10	$54.10	$54.10
Purchase #6	$214.46	11.391%	$238.8891	$238.89	$238.90	$238.90
Purchase #7	$166.29	9.349%	$181.8365	$181.84	$181.85	$181.80
7 purchase totals =	$646.80		$708.4772	$708.48	$708.45	$708.60