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	$50.79	6.846%	$54.2671	$54.27	$54.25	$54.30
Purchase #2	$11.68	3.583%	$12.0985	$12.10	$12.10	$12.10
Purchase #3	$14.36	12.392%	$16.1395	$16.14	$16.15	$16.10
Purchase #4	$244.98	7.144%	$262.4814	$262.48	$262.50	$262.50
Purchase #5	$81.73	9.488%	$89.4845	$89.48	$89.50	$89.50
Purchase #6	$194.52	11.277%	$216.456	$216.46	$216.45	$216.50
Purchase #7	$169.92	9.851%	$186.6588	$186.66	$186.65	$186.70
7 purchase totals =	$767.98		$837.5858	$837.59	$837.60	$837.70