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	$223.71	7.364%	$240.184	$240.18	$240.20	$240.20
Purchase #2	$232.31	7.824%	$250.4859	$250.49	$250.50	$250.50
Purchase #3	$81.86	4.669%	$85.682	$85.68	$85.70	$85.70
Purchase #4	$84.66	4.794%	$88.7186	$88.72	$88.70	$88.70
Purchase #5	$173.47	6.466%	$184.6866	$184.69	$184.70	$184.70
Purchase #6	$54.78	5.124%	$57.5869	$57.59	$57.60	$57.60
Purchase #7	$157.47	3.113%	$162.372	$162.37	$162.35	$162.40
7 purchase totals =	$1,008.26		$1,069.7160	$1,069.72	$1,069.75	$1,069.80