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	$196.78	11.356%	$219.1263	$219.13	$219.15	$219.10
Purchase #2	$194.90	7.644%	$209.7982	$209.80	$209.80	$209.80
Purchase #3	$148.77	4.487%	$155.4453	$155.45	$155.45	$155.40
Purchase #4	$78.88	8.668%	$85.7173	$85.72	$85.70	$85.70
Purchase #5	$204.65	3.396%	$211.5999	$211.60	$211.60	$211.60
Purchase #6	$204.39	3.586%	$211.7194	$211.72	$211.70	$211.70
Purchase #7	$128.55	13.164%	$145.4723	$145.47	$145.45	$145.50
7 purchase totals =	$1,156.92		$1,238.8787	$1,238.89	$1,238.85	$1,238.80