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	$157.57	10.612%	$174.2913	$174.29	$174.30	$174.30
Purchase #2	$131.42	10.153%	$144.7631	$144.76	$144.75	$144.80
Purchase #3	$63.89	3.389%	$66.0552	$66.06	$66.05	$66.10
Purchase #4	$135.67	13.137%	$153.493	$153.49	$153.50	$153.50
Purchase #5	$138.62	11.313%	$154.3021	$154.30	$154.30	$154.30
Purchase #6	$165.82	3.254%	$171.2158	$171.22	$171.20	$171.20
Purchase #7	$40.73	11.659%	$45.4787	$45.48	$45.50	$45.50
7 purchase totals =	$833.72		$909.5992	$909.60	$909.60	$909.70