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	$233.61	12.409%	$262.5987	$262.60	$262.60	$262.60
Purchase #2	$220.90	11.873%	$247.1275	$247.13	$247.15	$247.10
Purchase #3	$27.25	4.420%	$28.4545	$28.45	$28.45	$28.50
Purchase #4	$39.90	6.575%	$42.5234	$42.52	$42.50	$42.50
Purchase #5	$13.71	10.559%	$15.1576	$15.16	$15.15	$15.20
Purchase #6	$170.30	6.176%	$180.8177	$180.82	$180.80	$180.80
Purchase #7	$90.41	3.477%	$93.5536	$93.55	$93.55	$93.60
7 purchase totals =	$796.08		$870.2330	$870.23	$870.20	$870.30