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	$226.50	3.656%	$234.7808	$234.78	$234.80	$234.80
Purchase #2	$218.85	4.635%	$228.9937	$228.99	$229.00	$229.00
Purchase #3	$83.47	10.304%	$92.0707	$92.07	$92.05	$92.10
Purchase #4	$203.52	7.393%	$218.5662	$218.57	$218.55	$218.60
Purchase #5	$134.83	12.604%	$151.824	$151.82	$151.80	$151.80
Purchase #6	$49.80	10.751%	$55.154	$55.15	$55.15	$55.20
Purchase #7	$182.58	4.869%	$191.4698	$191.47	$191.45	$191.50
7 purchase totals =	$1,099.55		$1,172.8592	$1,172.85	$1,172.80	$1,173.00