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	$222.42	5.868%	$235.4716	$235.47	$235.45	$235.50
Purchase #2	$55.87	5.396%	$58.8847	$58.88	$58.90	$58.90
Purchase #3	$22.81	11.540%	$25.4423	$25.44	$25.45	$25.40
Purchase #4	$112.76	9.212%	$123.1475	$123.15	$123.15	$123.10
Purchase #5	$153.61	12.357%	$172.5916	$172.59	$172.60	$172.60
Purchase #6	$30.63	10.559%	$33.8642	$33.86	$33.85	$33.90
Purchase #7	$5.42	11.670%	$6.0525	$6.05	$6.05	$6.10
7 purchase totals =	$603.52		$655.4544	$655.44	$655.45	$655.50