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	$216.60	11.795%	$242.148	$242.15	$242.15	$242.10
Purchase #2	$172.68	6.742%	$184.3221	$184.32	$184.30	$184.30
Purchase #3	$13.42	4.374%	$14.007	$14.01	$14.00	$14.00
Purchase #4	$26.29	8.617%	$28.5554	$28.56	$28.55	$28.60
Purchase #5	$95.98	12.797%	$108.2626	$108.26	$108.25	$108.30
Purchase #6	$61.44	10.197%	$67.705	$67.71	$67.70	$67.70
Purchase #7	$49.59	8.618%	$53.8637	$53.86	$53.85	$53.90
7 purchase totals =	$636.00		$698.8638	$698.87	$698.80	$698.90