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	$159.87	13.197%	$180.968	$180.97	$180.95	$181.00
Purchase #2	$56.99	12.308%	$64.0043	$64.00	$64.00	$64.00
Purchase #3	$77.72	5.687%	$82.1399	$82.14	$82.15	$82.10
Purchase #4	$221.69	7.244%	$237.7492	$237.75	$237.75	$237.70
Purchase #5	$94.50	6.328%	$100.48	$100.48	$100.50	$100.50
Purchase #6	$84.67	5.552%	$89.3709	$89.37	$89.35	$89.40
Purchase #7	$165.74	7.677%	$178.4639	$178.46	$178.45	$178.50
7 purchase totals =	$861.18		$933.1762	$933.17	$933.15	$933.20