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	$179.60	7.327%	$192.7593	$192.76	$192.75	$192.80
Purchase #2	$92.90	13.733%	$105.658	$105.66	$105.65	$105.70
Purchase #3	$119.39	7.576%	$128.435	$128.44	$128.45	$128.40
Purchase #4	$80.87	10.159%	$89.0856	$89.09	$89.10	$89.10
Purchase #5	$60.55	10.691%	$67.0234	$67.02	$67.00	$67.00
Purchase #6	$34.71	12.486%	$39.0439	$39.04	$39.05	$39.00
Purchase #7	$24.29	13.107%	$27.4737	$27.47	$27.45	$27.50
7 purchase totals =	$592.31		$649.4789	$649.48	$649.45	$649.50