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	$200.41	3.609%	$207.6428	$207.64	$207.65	$207.60
Purchase #2	$79.88	7.605%	$85.9549	$85.95	$85.95	$86.00
Purchase #3	$185.82	4.641%	$194.4439	$194.44	$194.45	$194.40
Purchase #4	$153.37	4.253%	$159.8928	$159.89	$159.90	$159.90
Purchase #5	$244.40	5.794%	$258.5605	$258.56	$258.55	$258.60
Purchase #6	$77.27	10.595%	$85.4568	$85.46	$85.45	$85.50
Purchase #7	$243.93	3.263%	$251.8894	$251.89	$251.90	$251.90
7 purchase totals =	$1,185.08		$1,243.8411	$1,243.83	$1,243.85	$1,243.90