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	$103.97	4.108%	$108.2411	$108.24	$108.25	$108.20
Purchase #2	$85.83	4.766%	$89.9207	$89.92	$89.90	$89.90
Purchase #3	$228.41	11.632%	$254.9787	$254.98	$255.00	$255.00
Purchase #4	$95.38	11.191%	$106.054	$106.05	$106.05	$106.10
Purchase #5	$81.95	10.107%	$90.2327	$90.23	$90.25	$90.20
Purchase #6	$169.89	10.169%	$187.1661	$187.17	$187.15	$187.20
Purchase #7	$224.93	3.140%	$231.9928	$231.99	$232.00	$232.00
7 purchase totals =	$990.36		$1,068.5861	$1,068.58	$1,068.60	$1,068.60