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	$190.29	5.425%	$200.6132	$200.61	$200.60	$200.60
Purchase #2	$180.50	7.279%	$193.6386	$193.64	$193.65	$193.60
Purchase #3	$89.55	9.575%	$98.1244	$98.12	$98.10	$98.10
Purchase #4	$127.95	11.431%	$142.576	$142.58	$142.60	$142.60
Purchase #5	$67.87	9.249%	$74.1473	$74.15	$74.15	$74.10
Purchase #6	$94.72	13.467%	$107.4759	$107.48	$107.50	$107.50
Purchase #7	$32.55	13.866%	$37.0634	$37.06	$37.05	$37.10
7 purchase totals =	$783.43		$853.6388	$853.64	$853.65	$853.60