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	$101.64	10.414%	$112.2248	$112.22	$112.20	$112.20
Purchase #2	$42.28	9.866%	$46.4513	$46.45	$46.45	$46.50
Purchase #3	$32.72	7.292%	$35.1059	$35.11	$35.10	$35.10
Purchase #4	$245.77	3.347%	$253.9959	$254.00	$254.00	$254.00
Purchase #5	$167.25	4.103%	$174.1123	$174.11	$174.10	$174.10
Purchase #6	$103.33	5.644%	$109.1619	$109.16	$109.15	$109.20
Purchase #7	$7.30	3.316%	$7.5421	$7.54	$7.55	$7.50
7 purchase totals =	$700.29		$738.5942	$738.59	$738.55	$738.60