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	$117.73	8.626%	$127.8854	$127.89	$127.90	$127.90
Purchase #2	$189.25	9.794%	$207.7851	$207.79	$207.80	$207.80
Purchase #3	$11.82	5.198%	$12.4344	$12.43	$12.45	$12.40
Purchase #4	$56.75	4.393%	$59.243	$59.24	$59.25	$59.20
Purchase #5	$80.57	6.206%	$85.5702	$85.57	$85.55	$85.60
Purchase #6	$48.38	11.816%	$54.0966	$54.10	$54.10	$54.10
Purchase #7	$143.77	4.452%	$150.1706	$150.17	$150.15	$150.20
7 purchase totals =	$648.27		$697.1853	$697.19	$697.20	$697.20