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	$164.28	8.590%	$178.3917	$178.39	$178.40	$178.40
Purchase #2	$162.57	6.608%	$173.3126	$173.31	$173.30	$173.30
Purchase #3	$195.52	4.646%	$204.6039	$204.60	$204.60	$204.60
Purchase #4	$69.25	4.196%	$72.1557	$72.16	$72.15	$72.20
Purchase #5	$105.90	11.169%	$117.728	$117.73	$117.75	$117.70
Purchase #6	$169.53	3.542%	$175.5348	$175.53	$175.55	$175.50
Purchase #7	$82.62	3.779%	$85.7422	$85.74	$85.75	$85.70
7 purchase totals =	$949.67		$1,007.4689	$1,007.46	$1,007.50	$1,007.40