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	$168.37	10.113%	$185.3973	$185.40	$185.40	$185.40
Purchase #2	$132.28	10.710%	$146.4472	$146.45	$146.45	$146.40
Purchase #3	$113.29	13.721%	$128.8345	$128.83	$128.85	$128.80
Purchase #4	$20.46	9.254%	$22.3534	$22.35	$22.35	$22.40
Purchase #5	$98.30	13.190%	$111.2658	$111.27	$111.25	$111.30
Purchase #6	$90.82	10.657%	$100.4987	$100.50	$100.50	$100.50
Purchase #7	$32.53	12.382%	$36.5579	$36.56	$36.55	$36.60
7 purchase totals =	$656.05		$731.3548	$731.36	$731.35	$731.40