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	$71.72	7.255%	$76.9233	$76.92	$76.90	$76.90
Purchase #2	$213.38	4.720%	$223.4515	$223.45	$223.45	$223.50
Purchase #3	$60.77	8.379%	$65.8619	$65.86	$65.85	$65.90
Purchase #4	$227.60	10.851%	$252.2969	$252.30	$252.30	$252.30
Purchase #5	$86.48	7.120%	$92.6374	$92.64	$92.65	$92.60
Purchase #6	$115.60	13.456%	$131.1551	$131.16	$131.15	$131.20
Purchase #7	$213.84	6.255%	$227.2157	$227.22	$227.20	$227.20
7 purchase totals =	$989.39		$1,069.5418	$1,069.55	$1,069.50	$1,069.60