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	$208.29	6.751%	$222.3517	$222.35	$222.35	$222.40
Purchase #2	$71.91	9.706%	$78.8896	$78.89	$78.90	$78.90
Purchase #3	$103.35	3.494%	$106.961	$106.96	$106.95	$107.00
Purchase #4	$61.86	10.769%	$68.5217	$68.52	$68.50	$68.50
Purchase #5	$232.80	4.132%	$242.4193	$242.42	$242.40	$242.40
Purchase #6	$209.94	5.812%	$222.1417	$222.14	$222.15	$222.10
Purchase #7	$8.91	12.300%	$10.0059	$10.01	$10.00	$10.00
7 purchase totals =	$897.06		$951.2909	$951.29	$951.25	$951.30