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	$149.84	4.432%	$156.4809	$156.48	$156.50	$156.50
Purchase #2	$137.51	5.419%	$144.9617	$144.96	$144.95	$145.00
Purchase #3	$208.70	13.318%	$236.4947	$236.49	$236.50	$236.50
Purchase #4	$225.71	13.145%	$255.3796	$255.38	$255.40	$255.40
Purchase #5	$171.60	11.501%	$191.3357	$191.34	$191.35	$191.30
Purchase #6	$30.54	5.285%	$32.154	$32.15	$32.15	$32.20
Purchase #7	$241.30	6.784%	$257.6698	$257.67	$257.65	$257.70
7 purchase totals =	$1,165.20		$1,274.4764	$1,274.47	$1,274.50	$1,274.60