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	$111.93	3.131%	$115.4345	$115.43	$115.45	$115.40
Purchase #2	$104.97	5.255%	$110.4862	$110.49	$110.50	$110.50
Purchase #3	$119.35	6.527%	$127.14	$127.14	$127.15	$127.10
Purchase #4	$102.25	6.124%	$108.5118	$108.51	$108.50	$108.50
Purchase #5	$92.92	13.162%	$105.1501	$105.15	$105.15	$105.20
Purchase #6	$81.53	13.250%	$92.3327	$92.33	$92.35	$92.30
Purchase #7	$200.30	11.441%	$223.2163	$223.22	$223.20	$223.20
7 purchase totals =	$813.25		$882.2716	$882.27	$882.30	$882.20