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	$161.26	3.829%	$167.4346	$167.43	$167.45	$167.40
Purchase #2	$232.54	13.509%	$263.9538	$263.95	$263.95	$264.00
Purchase #3	$138.45	6.513%	$147.4672	$147.47	$147.45	$147.50
Purchase #4	$149.62	12.389%	$168.1564	$168.16	$168.15	$168.20
Purchase #5	$219.47	8.135%	$237.3239	$237.32	$237.30	$237.30
Purchase #6	$48.71	13.577%	$55.3234	$55.32	$55.30	$55.30
Purchase #7	$19.85	9.727%	$21.7808	$21.78	$21.80	$21.80
7 purchase totals =	$969.90		$1,061.4401	$1,061.43	$1,061.40	$1,061.50