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	$173.81	7.238%	$186.3904	$186.39	$186.40	$186.40
Purchase #2	$195.82	4.479%	$204.5908	$204.59	$204.60	$204.60
Purchase #3	$193.70	13.755%	$220.3434	$220.34	$220.35	$220.30
Purchase #4	$247.45	6.729%	$264.1009	$264.10	$264.10	$264.10
Purchase #5	$56.42	8.609%	$61.2772	$61.28	$61.30	$61.30
Purchase #6	$60.51	10.280%	$66.7304	$66.73	$66.75	$66.70
Purchase #7	$36.75	11.300%	$40.9028	$40.90	$40.90	$40.90
7 purchase totals =	$964.46		$1,044.3359	$1,044.33	$1,044.40	$1,044.30