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	$112.59	3.408%	$116.4271	$116.43	$116.45	$116.40
Purchase #2	$62.42	12.560%	$70.26	$70.26	$70.25	$70.30
Purchase #3	$59.94	4.595%	$62.6942	$62.69	$62.70	$62.70
Purchase #4	$147.33	8.791%	$160.2818	$160.28	$160.30	$160.30
Purchase #5	$85.97	4.472%	$89.8146	$89.81	$89.80	$89.80
Purchase #6	$44.47	8.515%	$48.2566	$48.26	$48.25	$48.30
Purchase #7	$159.38	9.255%	$174.1306	$174.13	$174.15	$174.10
7 purchase totals =	$672.10		$721.8649	$721.86	$721.90	$721.90