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	$60.27	12.849%	$68.0141	$68.01	$68.00	$68.00
Purchase #2	$145.41	3.519%	$150.527	$150.53	$150.55	$150.50
Purchase #3	$76.90	10.720%	$85.1437	$85.14	$85.15	$85.10
Purchase #4	$180.80	4.401%	$188.757	$188.76	$188.75	$188.80
Purchase #5	$172.56	10.482%	$190.6477	$190.65	$190.65	$190.60
Purchase #6	$191.79	13.259%	$217.2194	$217.22	$217.20	$217.20
Purchase #7	$152.95	10.370%	$168.8109	$168.81	$168.80	$168.80
7 purchase totals =	$980.68		$1,069.1198	$1,069.12	$1,069.10	$1,069.00