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	$59.27	4.854%	$62.147	$62.15	$62.15	$62.10
Purchase #2	$163.90	7.181%	$175.6697	$175.67	$175.65	$175.70
Purchase #3	$138.71	10.496%	$153.269	$153.27	$153.25	$153.30
Purchase #4	$47.64	13.218%	$53.9371	$53.94	$53.95	$53.90
Purchase #5	$233.60	7.155%	$250.3141	$250.31	$250.30	$250.30
Purchase #6	$93.56	9.669%	$102.6063	$102.61	$102.60	$102.60
Purchase #7	$49.33	10.869%	$54.6917	$54.69	$54.70	$54.70
7 purchase totals =	$786.01		$852.6349	$852.64	$852.60	$852.60