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	$116.83	5.446%	$123.1926	$123.19	$123.20	$123.20
Purchase #2	$234.36	7.625%	$252.23	$252.23	$252.25	$252.20
Purchase #3	$202.84	9.562%	$222.2356	$222.24	$222.25	$222.20
Purchase #4	$25.79	7.439%	$27.7085	$27.71	$27.70	$27.70
Purchase #5	$128.27	12.205%	$143.9254	$143.93	$143.95	$143.90
Purchase #6	$172.59	13.863%	$196.5162	$196.52	$196.50	$196.50
Purchase #7	$144.69	4.424%	$151.0911	$151.09	$151.10	$151.10
7 purchase totals =	$1,025.37		$1,116.8994	$1,116.91	$1,116.95	$1,116.80