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	$205.48	9.329%	$224.6492	$224.65	$224.65	$224.60
Purchase #2	$52.60	13.563%	$59.7341	$59.73	$59.75	$59.70
Purchase #3	$161.28	11.310%	$179.5208	$179.52	$179.50	$179.50
Purchase #4	$166.30	4.164%	$173.2247	$173.22	$173.20	$173.20
Purchase #5	$109.42	10.426%	$120.8281	$120.83	$120.85	$120.80
Purchase #6	$94.77	11.653%	$105.8135	$105.81	$105.80	$105.80
Purchase #7	$159.91	6.163%	$169.7653	$169.77	$169.75	$169.80
7 purchase totals =	$949.76		$1,033.5357	$1,033.53	$1,033.50	$1,033.40