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	$95.31	9.199%	$104.0776	$104.08	$104.10	$104.10
Purchase #2	$167.54	7.198%	$179.5995	$179.60	$179.60	$179.60
Purchase #3	$227.64	10.835%	$252.3048	$252.30	$252.30	$252.30
Purchase #4	$77.35	8.503%	$83.9271	$83.93	$83.95	$83.90
Purchase #5	$161.59	13.397%	$183.2382	$183.24	$183.25	$183.20
Purchase #6	$56.48	4.705%	$59.1374	$59.14	$59.15	$59.10
Purchase #7	$74.75	11.761%	$83.5413	$83.54	$83.55	$83.50
7 purchase totals =	$860.66		$945.8259	$945.83	$945.90	$945.70