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	$162.50	6.238%	$172.6368	$172.64	$172.65	$172.60
Purchase #2	$189.84	7.473%	$204.0267	$204.03	$204.05	$204.00
Purchase #3	$145.44	8.814%	$158.2591	$158.26	$158.25	$158.30
Purchase #4	$128.48	7.110%	$137.6149	$137.61	$137.60	$137.60
Purchase #5	$105.54	12.739%	$118.9847	$118.98	$119.00	$119.00
Purchase #6	$59.35	10.116%	$65.3538	$65.35	$65.35	$65.40
Purchase #7	$32.75	7.330%	$35.1506	$35.15	$35.15	$35.20
7 purchase totals =	$823.90		$892.0266	$892.02	$892.05	$892.10