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	$125.59	4.714%	$131.5103	$131.51	$131.50	$131.50
Purchase #2	$79.25	3.612%	$82.1125	$82.11	$82.10	$82.10
Purchase #3	$102.83	4.842%	$107.809	$107.81	$107.80	$107.80
Purchase #4	$20.35	10.481%	$22.4829	$22.48	$22.50	$22.50
Purchase #5	$42.85	5.152%	$45.0576	$45.06	$45.05	$45.10
Purchase #6	$163.50	11.193%	$181.8006	$181.80	$181.80	$181.80
Purchase #7	$106.35	12.111%	$119.23	$119.23	$119.25	$119.20
7 purchase totals =	$640.72		$690.0029	$690.00	$690.00	$690.00