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	$38.81	7.335%	$41.6567	$41.66	$41.65	$41.70
Purchase #2	$173.51	9.619%	$190.1999	$190.20	$190.20	$190.20
Purchase #3	$19.51	11.437%	$21.7414	$21.74	$21.75	$21.70
Purchase #4	$75.40	9.404%	$82.4906	$82.49	$82.50	$82.50
Purchase #5	$6.52	3.530%	$6.7502	$6.75	$6.75	$6.80
Purchase #6	$117.58	8.649%	$127.7495	$127.75	$127.75	$127.70
Purchase #7	$176.57	11.494%	$196.865	$196.87	$196.85	$196.90
7 purchase totals =	$607.90		$667.4533	$667.46	$667.45	$667.50