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	$184.69	6.319%	$196.3606	$196.36	$196.35	$196.40
Purchase #2	$112.40	4.139%	$117.0522	$117.05	$117.05	$117.10
Purchase #3	$117.73	11.153%	$130.8604	$130.86	$130.85	$130.90
Purchase #4	$230.93	8.729%	$251.0879	$251.09	$251.10	$251.10
Purchase #5	$79.95	13.346%	$90.6201	$90.62	$90.60	$90.60
Purchase #6	$116.84	10.349%	$128.9318	$128.93	$128.95	$128.90
Purchase #7	$87.99	8.660%	$95.6099	$95.61	$95.60	$95.60
7 purchase totals =	$930.53		$1,010.5229	$1,010.52	$1,010.50	$1,010.60