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	$112.90	4.601%	$118.0945	$118.09	$118.10	$118.10
Purchase #2	$231.39	13.626%	$262.9192	$262.92	$262.90	$262.90
Purchase #3	$157.33	6.361%	$167.3378	$167.34	$167.35	$167.30
Purchase #4	$109.90	5.821%	$116.2973	$116.30	$116.30	$116.30
Purchase #5	$133.41	3.828%	$138.5169	$138.52	$138.50	$138.50
Purchase #6	$57.31	9.810%	$62.9321	$62.93	$62.95	$62.90
Purchase #7	$199.38	5.392%	$210.1306	$210.13	$210.15	$210.10
7 purchase totals =	$1,001.62		$1,076.2284	$1,076.23	$1,076.25	$1,076.10