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	$172.87	3.468%	$178.8651	$178.87	$178.85	$178.90
Purchase #2	$217.88	9.304%	$238.1516	$238.15	$238.15	$238.20
Purchase #3	$197.60	4.106%	$205.7135	$205.71	$205.70	$205.70
Purchase #4	$71.98	5.726%	$76.1016	$76.10	$76.10	$76.10
Purchase #5	$139.78	6.701%	$149.1467	$149.15	$149.15	$149.10
Purchase #6	$150.54	9.792%	$165.2809	$165.28	$165.30	$165.30
Purchase #7	$232.70	4.155%	$242.3687	$242.37	$242.35	$242.40
7 purchase totals =	$1,183.35		$1,255.6281	$1,255.63	$1,255.60	$1,255.70