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	$148.32	7.185%	$158.9768	$158.98	$159.00	$159.00
Purchase #2	$50.41	5.582%	$53.2239	$53.22	$53.20	$53.20
Purchase #3	$74.59	4.575%	$78.0025	$78.00	$78.00	$78.00
Purchase #4	$123.41	12.784%	$139.1867	$139.19	$139.20	$139.20
Purchase #5	$99.92	10.334%	$110.2457	$110.25	$110.25	$110.20
Purchase #6	$190.86	9.291%	$208.5928	$208.59	$208.60	$208.60
Purchase #7	$148.65	6.235%	$157.9183	$157.92	$157.90	$157.90
7 purchase totals =	$836.16		$906.1467	$906.15	$906.15	$906.10