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	$247.35	12.655%	$278.6521	$278.65	$278.65	$278.70
Purchase #2	$8.66	3.180%	$8.9354	$8.94	$8.95	$8.90
Purchase #3	$214.83	12.695%	$242.1027	$242.10	$242.10	$242.10
Purchase #4	$141.73	6.257%	$150.598	$150.60	$150.60	$150.60
Purchase #5	$93.72	10.409%	$103.4753	$103.48	$103.50	$103.50
Purchase #6	$90.42	8.483%	$98.0903	$98.09	$98.10	$98.10
Purchase #7	$114.53	11.713%	$127.9449	$127.94	$127.95	$127.90
7 purchase totals =	$911.24		$1,009.7987	$1,009.80	$1,009.85	$1,009.80