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	$112.49	7.466%	$120.8885	$120.89	$120.90	$120.90
Purchase #2	$113.28	13.339%	$128.3904	$128.39	$128.40	$128.40
Purchase #3	$222.60	4.798%	$233.2803	$233.28	$233.30	$233.30
Purchase #4	$201.86	11.503%	$225.08	$225.08	$225.10	$225.10
Purchase #5	$98.54	12.842%	$111.1945	$111.19	$111.20	$111.20
Purchase #6	$147.73	10.429%	$163.1368	$163.14	$163.15	$163.10
Purchase #7	$108.29	7.597%	$116.5168	$116.52	$116.50	$116.50
7 purchase totals =	$1,004.79		$1,098.4873	$1,098.49	$1,098.55	$1,098.50