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	$191.54	9.359%	$209.4662	$209.47	$209.45	$209.50
Purchase #2	$181.54	12.113%	$203.5299	$203.53	$203.55	$203.50
Purchase #3	$15.55	6.815%	$16.6097	$16.61	$16.60	$16.60
Purchase #4	$10.74	5.129%	$11.2909	$11.29	$11.30	$11.30
Purchase #5	$118.77	12.681%	$133.8312	$133.83	$133.85	$133.80
Purchase #6	$57.99	3.275%	$59.8892	$59.89	$59.90	$59.90
Purchase #7	$105.32	5.540%	$111.1547	$111.15	$111.15	$111.20
7 purchase totals =	$681.45		$745.7718	$745.77	$745.80	$745.80