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	$137.42	4.328%	$143.3675	$143.37	$143.35	$143.40
Purchase #2	$49.32	7.595%	$53.0659	$53.07	$53.05	$53.10
Purchase #3	$185.85	13.806%	$211.5085	$211.51	$211.50	$211.50
Purchase #4	$120.34	7.115%	$128.9022	$128.90	$128.90	$128.90
Purchase #5	$190.95	8.141%	$206.4952	$206.50	$206.50	$206.50
Purchase #6	$230.37	12.627%	$259.4588	$259.46	$259.45	$259.50
Purchase #7	$159.32	10.334%	$175.7841	$175.78	$175.80	$175.80
7 purchase totals =	$1,073.57		$1,178.5822	$1,178.59	$1,178.55	$1,178.70