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	$185.99	5.720%	$196.6286	$196.63	$196.65	$196.60
Purchase #2	$163.44	13.594%	$185.658	$185.66	$185.65	$185.70
Purchase #3	$145.33	9.221%	$158.7309	$158.73	$158.75	$158.70
Purchase #4	$41.96	3.516%	$43.4353	$43.44	$43.45	$43.40
Purchase #5	$18.76	7.453%	$20.1582	$20.16	$20.15	$20.20
Purchase #6	$50.70	4.839%	$53.1534	$53.15	$53.15	$53.20
Purchase #7	$46.90	7.345%	$50.3448	$50.34	$50.35	$50.30
7 purchase totals =	$653.08		$708.1092	$708.11	$708.15	$708.10