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	$183.53	3.765%	$190.4399	$190.44	$190.45	$190.40
Purchase #2	$85.31	10.839%	$94.5568	$94.56	$94.55	$94.60
Purchase #3	$91.99	8.335%	$99.6574	$99.66	$99.65	$99.70
Purchase #4	$106.72	10.576%	$118.0067	$118.01	$118.00	$118.00
Purchase #5	$42.79	5.784%	$45.265	$45.27	$45.25	$45.30
Purchase #6	$123.89	5.621%	$130.8539	$130.85	$130.85	$130.90
Purchase #7	$84.35	10.841%	$93.4944	$93.49	$93.50	$93.50
7 purchase totals =	$718.58		$772.2741	$772.28	$772.25	$772.40