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	$116.40	5.366%	$122.646	$122.65	$122.65	$122.60
Purchase #2	$173.67	4.861%	$182.1121	$182.11	$182.10	$182.10
Purchase #3	$55.42	13.566%	$62.9383	$62.94	$62.95	$62.90
Purchase #4	$25.42	9.277%	$27.7782	$27.78	$27.80	$27.80
Purchase #5	$231.38	5.277%	$243.5899	$243.59	$243.60	$243.60
Purchase #6	$70.58	11.399%	$78.6254	$78.63	$78.65	$78.60
Purchase #7	$152.47	4.218%	$158.9012	$158.90	$158.90	$158.90
7 purchase totals =	$825.34		$876.5911	$876.60	$876.65	$876.50