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	$144.84	8.335%	$156.9124	$156.91	$156.90	$156.90
Purchase #2	$9.48	9.198%	$10.352	$10.35	$10.35	$10.40
Purchase #3	$156.35	4.124%	$162.7979	$162.80	$162.80	$162.80
Purchase #4	$91.34	9.826%	$100.3151	$100.32	$100.30	$100.30
Purchase #5	$236.36	5.470%	$249.2889	$249.29	$249.30	$249.30
Purchase #6	$247.86	11.223%	$275.6773	$275.68	$275.70	$275.70
Purchase #7	$44.25	10.329%	$48.8206	$48.82	$48.80	$48.80
7 purchase totals =	$930.48		$1,004.1642	$1,004.17	$1,004.15	$1,004.20