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	$65.90	11.467%	$73.4568	$73.46	$73.45	$73.50
Purchase #2	$15.29	4.485%	$15.9758	$15.98	$16.00	$16.00
Purchase #3	$82.91	7.548%	$89.168	$89.17	$89.15	$89.20
Purchase #4	$58.76	7.454%	$63.14	$63.14	$63.15	$63.10
Purchase #5	$178.34	7.503%	$191.7209	$191.72	$191.70	$191.70
Purchase #6	$13.45	7.837%	$14.5041	$14.50	$14.50	$14.50
Purchase #7	$153.64	13.788%	$174.8239	$174.82	$174.80	$174.80
7 purchase totals =	$568.29		$622.7895	$622.79	$622.75	$622.80