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	$144.88	7.704%	$156.0416	$156.04	$156.05	$156.00
Purchase #2	$142.60	7.796%	$153.7171	$153.72	$153.70	$153.70
Purchase #3	$165.89	6.194%	$176.1652	$176.17	$176.15	$176.20
Purchase #4	$95.91	10.128%	$105.6238	$105.62	$105.60	$105.60
Purchase #5	$33.31	5.560%	$35.162	$35.16	$35.15	$35.20
Purchase #6	$161.29	12.138%	$180.8674	$180.87	$180.85	$180.90
Purchase #7	$91.86	10.512%	$101.5163	$101.52	$101.50	$101.50
7 purchase totals =	$835.74		$909.0934	$909.10	$909.00	$909.10