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	$104.96	6.655%	$111.9451	$111.95	$111.95	$111.90
Purchase #2	$48.45	6.586%	$51.6409	$51.64	$51.65	$51.60
Purchase #3	$128.59	6.667%	$137.1631	$137.16	$137.15	$137.20
Purchase #4	$12.33	13.684%	$14.0172	$14.02	$14.00	$14.00
Purchase #5	$248.68	10.314%	$274.3289	$274.33	$274.35	$274.30
Purchase #6	$117.82	9.646%	$129.1849	$129.18	$129.20	$129.20
Purchase #7	$112.56	3.142%	$116.0966	$116.10	$116.10	$116.10
7 purchase totals =	$773.39		$834.3767	$834.38	$834.40	$834.30