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	$65.56	7.398%	$70.4101	$70.41	$70.40	$70.40
Purchase #2	$5.82	5.371%	$6.1326	$6.13	$6.15	$6.10
Purchase #3	$31.85	4.537%	$33.295	$33.30	$33.30	$33.30
Purchase #4	$108.27	13.482%	$122.867	$122.87	$122.85	$122.90
Purchase #5	$40.50	11.418%	$45.1243	$45.12	$45.10	$45.10
Purchase #6	$197.59	13.325%	$223.9189	$223.92	$223.90	$223.90
Purchase #7	$214.55	4.259%	$223.6877	$223.69	$223.70	$223.70
7 purchase totals =	$664.14		$725.4356	$725.44	$725.40	$725.40