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	$34.25	11.136%	$38.0641	$38.06	$38.05	$38.10
Purchase #2	$13.73	6.344%	$14.601	$14.60	$14.60	$14.60
Purchase #3	$139.45	9.840%	$153.1719	$153.17	$153.15	$153.20
Purchase #4	$42.34	7.792%	$45.6391	$45.64	$45.65	$45.60
Purchase #5	$62.96	10.571%	$69.6155	$69.62	$69.60	$69.60
Purchase #6	$128.25	11.802%	$143.3861	$143.39	$143.40	$143.40
Purchase #7	$114.72	5.414%	$120.9309	$120.93	$120.95	$120.90
7 purchase totals =	$535.70		$585.4086	$585.41	$585.40	$585.40