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	$115.49	13.490%	$131.0696	$131.07	$131.05	$131.10
Purchase #2	$153.27	9.111%	$167.2344	$167.23	$167.25	$167.20
Purchase #3	$65.35	10.373%	$72.1288	$72.13	$72.15	$72.10
Purchase #4	$153.69	12.756%	$173.2947	$173.29	$173.30	$173.30
Purchase #5	$102.48	5.739%	$108.3613	$108.36	$108.35	$108.40
Purchase #6	$165.42	8.542%	$179.5502	$179.55	$179.55	$179.60
Purchase #7	$223.49	6.233%	$237.4201	$237.42	$237.40	$237.40
7 purchase totals =	$979.19		$1,069.0591	$1,069.05	$1,069.05	$1,069.10