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	$165.59	4.351%	$172.7948	$172.79	$172.80	$172.80
Purchase #2	$35.73	11.203%	$39.7328	$39.73	$39.75	$39.70
Purchase #3	$171.57	8.114%	$185.4912	$185.49	$185.50	$185.50
Purchase #4	$157.36	13.495%	$178.5957	$178.60	$178.60	$178.60
Purchase #5	$242.78	12.546%	$273.2392	$273.24	$273.25	$273.20
Purchase #6	$59.58	12.546%	$67.0549	$67.05	$67.05	$67.10
Purchase #7	$238.49	6.838%	$254.7979	$254.80	$254.80	$254.80
7 purchase totals =	$1,071.10		$1,171.7065	$1,171.70	$1,171.75	$1,171.70