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	$214.57	6.333%	$228.1587	$228.16	$228.15	$228.20
Purchase #2	$76.52	7.363%	$82.1542	$82.15	$82.15	$82.20
Purchase #3	$205.27	10.574%	$226.9752	$226.98	$227.00	$227.00
Purchase #4	$94.61	12.619%	$106.5488	$106.55	$106.55	$106.50
Purchase #5	$69.33	4.601%	$72.5199	$72.52	$72.50	$72.50
Purchase #6	$214.45	11.374%	$238.8415	$238.84	$238.85	$238.80
Purchase #7	$188.73	13.513%	$214.2331	$214.23	$214.25	$214.20
7 purchase totals =	$1,063.48		$1,169.4314	$1,169.43	$1,169.45	$1,169.40