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	$135.27	9.759%	$148.471	$148.47	$148.45	$148.50
Purchase #2	$84.46	9.641%	$92.6028	$92.60	$92.60	$92.60
Purchase #3	$211.27	5.137%	$222.1229	$222.12	$222.10	$222.10
Purchase #4	$13.72	13.540%	$15.5777	$15.58	$15.60	$15.60
Purchase #5	$247.46	7.747%	$266.6307	$266.63	$266.65	$266.60
Purchase #6	$186.57	3.704%	$193.4806	$193.48	$193.50	$193.50
Purchase #7	$84.63	7.466%	$90.9485	$90.95	$90.95	$90.90
7 purchase totals =	$963.38		$1,029.8342	$1,029.83	$1,029.85	$1,029.80