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	$169.31	5.644%	$178.8659	$178.87	$178.85	$178.90
Purchase #2	$192.28	4.110%	$200.1827	$200.18	$200.20	$200.20
Purchase #3	$85.56	8.397%	$92.7445	$92.74	$92.75	$92.70
Purchase #4	$145.29	3.344%	$150.1485	$150.15	$150.15	$150.10
Purchase #5	$90.54	9.418%	$99.0671	$99.07	$99.05	$99.10
Purchase #6	$35.70	5.335%	$37.6046	$37.60	$37.60	$37.60
Purchase #7	$16.50	4.869%	$17.3034	$17.30	$17.30	$17.30
7 purchase totals =	$735.18		$775.9167	$775.91	$775.90	$775.90