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	$160.89	11.277%	$179.0336	$179.03	$179.05	$179.00
Purchase #2	$175.37	8.500%	$190.2765	$190.28	$190.30	$190.30
Purchase #3	$146.42	11.328%	$163.0065	$163.01	$163.00	$163.00
Purchase #4	$129.89	12.851%	$146.5822	$146.58	$146.60	$146.60
Purchase #5	$91.42	10.472%	$100.9935	$100.99	$101.00	$101.00
Purchase #6	$85.71	4.230%	$89.3355	$89.34	$89.35	$89.30
Purchase #7	$139.73	11.245%	$155.4426	$155.44	$155.45	$155.40
7 purchase totals =	$929.43		$1,024.6704	$1,024.67	$1,024.75	$1,024.60