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	$156.35	6.516%	$166.5378	$166.54	$166.55	$166.50
Purchase #2	$35.39	7.301%	$37.9738	$37.97	$37.95	$38.00
Purchase #3	$174.80	12.131%	$196.005	$196.01	$196.00	$196.00
Purchase #4	$140.80	12.431%	$158.3028	$158.30	$158.30	$158.30
Purchase #5	$192.40	12.531%	$216.5096	$216.51	$216.50	$216.50
Purchase #6	$111.65	7.103%	$119.5805	$119.58	$119.60	$119.60
Purchase #7	$165.81	5.617%	$175.1235	$175.12	$175.10	$175.10
7 purchase totals =	$977.20		$1,070.0330	$1,070.03	$1,070.00	$1,070.00