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	$98.49	13.670%	$111.9536	$111.95	$111.95	$112.00
Purchase #2	$158.27	9.535%	$173.361	$173.36	$173.35	$173.40
Purchase #3	$49.78	7.156%	$53.3423	$53.34	$53.35	$53.30
Purchase #4	$108.28	12.157%	$121.4436	$121.44	$121.45	$121.40
Purchase #5	$53.92	9.720%	$59.161	$59.16	$59.15	$59.20
Purchase #6	$148.25	11.606%	$165.4559	$165.46	$165.45	$165.50
Purchase #7	$133.85	6.762%	$142.9009	$142.90	$142.90	$142.90
7 purchase totals =	$750.84		$827.6183	$827.61	$827.60	$827.70