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	$211.93	12.192%	$237.7685	$237.77	$237.75	$237.80
Purchase #2	$33.47	13.136%	$37.8666	$37.87	$37.85	$37.90
Purchase #3	$16.42	13.511%	$18.6385	$18.64	$18.65	$18.60
Purchase #4	$231.63	7.852%	$249.8176	$249.82	$249.80	$249.80
Purchase #5	$57.73	3.698%	$59.8649	$59.86	$59.85	$59.90
Purchase #6	$186.68	3.583%	$193.3687	$193.37	$193.35	$193.40
Purchase #7	$196.95	9.457%	$215.5756	$215.58	$215.60	$215.60
7 purchase totals =	$934.81		$1,012.9004	$1,012.91	$1,012.85	$1,013.00