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	$148.82	10.687%	$164.7244	$164.72	$164.70	$164.70
Purchase #2	$14.98	13.641%	$17.0234	$17.02	$17.00	$17.00
Purchase #3	$228.48	9.674%	$250.5832	$250.58	$250.60	$250.60
Purchase #4	$188.57	4.346%	$196.7653	$196.77	$196.75	$196.80
Purchase #5	$107.78	5.367%	$113.5646	$113.56	$113.55	$113.60
Purchase #6	$150.90	5.145%	$158.6638	$158.66	$158.65	$158.70
Purchase #7	$220.50	4.486%	$230.3916	$230.39	$230.40	$230.40
7 purchase totals =	$1,060.03		$1,131.7163	$1,131.70	$1,131.65	$1,131.80