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	$9.52	12.835%	$10.7419	$10.74	$10.75	$10.70
Purchase #2	$214.85	3.455%	$222.2731	$222.27	$222.25	$222.30
Purchase #3	$218.43	13.517%	$247.9552	$247.96	$247.95	$248.00
Purchase #4	$209.78	5.872%	$222.0983	$222.10	$222.10	$222.10
Purchase #5	$54.42	5.799%	$57.5758	$57.58	$57.60	$57.60
Purchase #6	$234.56	9.841%	$257.643	$257.64	$257.65	$257.60
Purchase #7	$99.33	9.622%	$108.8875	$108.89	$108.90	$108.90
7 purchase totals =	$1,040.89		$1,127.1748	$1,127.18	$1,127.20	$1,127.20