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	$158.37	8.256%	$171.445	$171.45	$171.45	$171.40
Purchase #2	$202.77	10.271%	$223.5965	$223.60	$223.60	$223.60
Purchase #3	$189.85	4.405%	$198.2129	$198.21	$198.20	$198.20
Purchase #4	$11.89	5.411%	$12.5334	$12.53	$12.55	$12.50
Purchase #5	$130.73	10.682%	$144.6946	$144.69	$144.70	$144.70
Purchase #6	$163.83	3.521%	$169.5985	$169.60	$169.60	$169.60
Purchase #7	$81.67	6.283%	$86.8013	$86.80	$86.80	$86.80
7 purchase totals =	$939.11		$1,006.8822	$1,006.88	$1,006.90	$1,006.80