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	$214.88	11.134%	$238.8047	$238.80	$238.80	$238.80
Purchase #2	$40.29	8.747%	$43.8142	$43.81	$43.80	$43.80
Purchase #3	$53.30	11.534%	$59.4476	$59.45	$59.45	$59.40
Purchase #4	$168.62	10.656%	$186.5881	$186.59	$186.60	$186.60
Purchase #5	$172.49	9.640%	$189.118	$189.12	$189.10	$189.10
Purchase #6	$31.55	4.454%	$32.9552	$32.96	$32.95	$33.00
Purchase #7	$41.26	3.644%	$42.7635	$42.76	$42.75	$42.80
7 purchase totals =	$722.39		$793.4913	$793.49	$793.45	$793.50