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	$172.49	11.595%	$192.4902	$192.49	$192.50	$192.50
Purchase #2	$211.80	8.774%	$230.3833	$230.38	$230.40	$230.40
Purchase #3	$103.28	8.334%	$111.8874	$111.89	$111.90	$111.90
Purchase #4	$74.41	8.499%	$80.7341	$80.73	$80.75	$80.70
Purchase #5	$74.46	12.588%	$83.833	$83.83	$83.85	$83.80
Purchase #6	$55.75	10.259%	$61.4694	$61.47	$61.45	$61.50
Purchase #7	$99.87	8.607%	$108.4658	$108.47	$108.45	$108.50
7 purchase totals =	$792.06		$869.2632	$869.26	$869.30	$869.30