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	$95.37	10.836%	$105.7043	$105.70	$105.70	$105.70
Purchase #2	$142.88	6.561%	$152.2544	$152.25	$152.25	$152.30
Purchase #3	$217.76	13.874%	$247.972	$247.97	$247.95	$248.00
Purchase #4	$188.95	10.671%	$209.1129	$209.11	$209.10	$209.10
Purchase #5	$146.54	8.839%	$159.4927	$159.49	$159.50	$159.50
Purchase #6	$61.47	9.243%	$67.1517	$67.15	$67.15	$67.20
Purchase #7	$69.95	10.285%	$77.1444	$77.14	$77.15	$77.10
7 purchase totals =	$922.92		$1,018.8324	$1,018.81	$1,018.80	$1,018.90