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	$162.90	5.291%	$171.519	$171.52	$171.50	$171.50
Purchase #2	$37.91	11.121%	$42.126	$42.13	$42.15	$42.10
Purchase #3	$54.74	11.204%	$60.8731	$60.87	$60.85	$60.90
Purchase #4	$225.74	6.419%	$240.2303	$240.23	$240.25	$240.20
Purchase #5	$90.78	5.622%	$95.8837	$95.88	$95.90	$95.90
Purchase #6	$212.26	9.116%	$231.6096	$231.61	$231.60	$231.60
Purchase #7	$189.81	3.697%	$196.8273	$196.83	$196.85	$196.80
7 purchase totals =	$974.14		$1,039.0690	$1,039.07	$1,039.10	$1,039.00