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	$132.64	6.863%	$141.7431	$141.74	$141.75	$141.70
Purchase #2	$215.42	3.426%	$222.8003	$222.80	$222.80	$222.80
Purchase #3	$233.47	13.554%	$265.1145	$265.11	$265.10	$265.10
Purchase #4	$163.41	12.518%	$183.8657	$183.87	$183.85	$183.90
Purchase #5	$173.91	9.552%	$190.5219	$190.52	$190.50	$190.50
Purchase #6	$38.69	5.754%	$40.9162	$40.92	$40.90	$40.90
Purchase #7	$100.99	5.312%	$106.3546	$106.35	$106.35	$106.40
7 purchase totals =	$1,058.53		$1,151.3163	$1,151.31	$1,151.25	$1,151.30