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	$139.97	10.695%	$154.9398	$154.94	$154.95	$154.90
Purchase #2	$93.83	6.628%	$100.0491	$100.05	$100.05	$100.00
Purchase #3	$27.35	7.605%	$29.43	$29.43	$29.45	$29.40
Purchase #4	$9.39	13.406%	$10.6488	$10.65	$10.65	$10.60
Purchase #5	$70.57	3.178%	$72.8127	$72.81	$72.80	$72.80
Purchase #6	$178.81	5.408%	$188.48	$188.48	$188.50	$188.50
Purchase #7	$125.96	3.391%	$130.2313	$130.23	$130.25	$130.20
7 purchase totals =	$645.88		$686.5917	$686.59	$686.65	$686.40