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	$159.47	3.851%	$165.6112	$165.61	$165.60	$165.60
Purchase #2	$71.45	3.252%	$73.7736	$73.77	$73.75	$73.80
Purchase #3	$53.27	11.332%	$59.3066	$59.31	$59.30	$59.30
Purchase #4	$184.29	10.376%	$203.4119	$203.41	$203.40	$203.40
Purchase #5	$132.72	10.412%	$146.5388	$146.54	$146.55	$146.50
Purchase #6	$148.92	5.366%	$156.911	$156.91	$156.90	$156.90
Purchase #7	$138.93	10.650%	$153.726	$153.73	$153.75	$153.70
7 purchase totals =	$889.05		$959.2791	$959.28	$959.25	$959.20