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	$123.75	8.501%	$134.27	$134.27	$134.25	$134.30
Purchase #2	$207.57	6.828%	$221.7429	$221.74	$221.75	$221.70
Purchase #3	$220.56	12.103%	$247.2544	$247.25	$247.25	$247.30
Purchase #4	$136.46	4.320%	$142.3551	$142.36	$142.35	$142.40
Purchase #5	$127.66	11.447%	$142.2732	$142.27	$142.25	$142.30
Purchase #6	$21.69	11.376%	$24.1575	$24.16	$24.15	$24.20
Purchase #7	$84.78	12.192%	$95.1164	$95.12	$95.10	$95.10
7 purchase totals =	$922.47		$1,007.1695	$1,007.17	$1,007.10	$1,007.30