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	$72.72	6.376%	$77.3566	$77.36	$77.35	$77.40
Purchase #2	$214.74	3.571%	$222.4084	$222.41	$222.40	$222.40
Purchase #3	$198.50	6.604%	$211.6089	$211.61	$211.60	$211.60
Purchase #4	$154.39	11.750%	$172.5308	$172.53	$172.55	$172.50
Purchase #5	$77.41	6.372%	$82.3426	$82.34	$82.35	$82.30
Purchase #6	$236.91	7.782%	$255.3463	$255.35	$255.35	$255.30
Purchase #7	$196.87	3.420%	$203.603	$203.60	$203.60	$203.60
7 purchase totals =	$1,151.54		$1,225.1966	$1,225.20	$1,225.20	$1,225.10