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	$69.40	12.577%	$78.1284	$78.13	$78.15	$78.10
Purchase #2	$216.31	8.460%	$234.6098	$234.61	$234.60	$234.60
Purchase #3	$39.68	7.835%	$42.7889	$42.79	$42.80	$42.80
Purchase #4	$166.36	3.177%	$171.6453	$171.65	$171.65	$171.60
Purchase #5	$37.85	4.248%	$39.4579	$39.46	$39.45	$39.50
Purchase #6	$245.55	3.499%	$254.1418	$254.14	$254.15	$254.10
Purchase #7	$238.57	10.176%	$262.8469	$262.85	$262.85	$262.80
7 purchase totals =	$1,013.72		$1,083.6190	$1,083.63	$1,083.65	$1,083.50