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	$175.72	4.399%	$183.4499	$183.45	$183.45	$183.40
Purchase #2	$27.80	5.156%	$29.2334	$29.23	$29.25	$29.20
Purchase #3	$79.91	11.298%	$88.9382	$88.94	$88.95	$88.90
Purchase #4	$172.40	13.814%	$196.2153	$196.22	$196.20	$196.20
Purchase #5	$171.92	12.417%	$193.2673	$193.27	$193.25	$193.30
Purchase #6	$95.89	11.595%	$107.0084	$107.01	$107.00	$107.00
Purchase #7	$152.91	3.622%	$158.4484	$158.45	$158.45	$158.40
7 purchase totals =	$876.55		$956.5609	$956.57	$956.55	$956.40