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	$162.92	6.449%	$173.4267	$173.43	$173.45	$173.40
Purchase #2	$214.56	4.545%	$224.3118	$224.31	$224.30	$224.30
Purchase #3	$144.75	3.704%	$150.1115	$150.11	$150.10	$150.10
Purchase #4	$229.76	11.177%	$255.4403	$255.44	$255.45	$255.40
Purchase #5	$131.25	8.566%	$142.4929	$142.49	$142.50	$142.50
Purchase #6	$192.53	8.826%	$209.5227	$209.52	$209.50	$209.50
Purchase #7	$91.84	3.682%	$95.2215	$95.22	$95.20	$95.20
7 purchase totals =	$1,167.61		$1,250.5274	$1,250.52	$1,250.50	$1,250.40