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	$78.78	8.849%	$85.7512	$85.75	$85.75	$85.80
Purchase #2	$105.25	10.315%	$116.1065	$116.11	$116.10	$116.10
Purchase #3	$190.44	11.214%	$211.7959	$211.80	$211.80	$211.80
Purchase #4	$82.85	8.803%	$90.1433	$90.14	$90.15	$90.10
Purchase #5	$72.39	6.866%	$77.3603	$77.36	$77.35	$77.40
Purchase #6	$198.41	4.657%	$207.65	$207.65	$207.65	$207.70
Purchase #7	$217.42	6.140%	$230.7696	$230.77	$230.75	$230.80
7 purchase totals =	$945.54		$1,019.5768	$1,019.58	$1,019.55	$1,019.70