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	$157.63	4.765%	$165.1411	$165.14	$165.15	$165.10
Purchase #2	$168.70	8.559%	$183.139	$183.14	$183.15	$183.10
Purchase #3	$33.90	5.162%	$35.6499	$35.65	$35.65	$35.60
Purchase #4	$71.46	11.770%	$79.8708	$79.87	$79.85	$79.90
Purchase #5	$13.61	5.787%	$14.3976	$14.40	$14.40	$14.40
Purchase #6	$194.52	3.259%	$200.8594	$200.86	$200.85	$200.90
Purchase #7	$54.68	3.328%	$56.4998	$56.50	$56.50	$56.50
7 purchase totals =	$694.50		$735.5576	$735.56	$735.55	$735.50