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	$71.94	12.195%	$80.7131	$80.71	$80.70	$80.70
Purchase #2	$242.69	3.546%	$251.2958	$251.30	$251.30	$251.30
Purchase #3	$46.41	13.120%	$52.499	$52.50	$52.50	$52.50
Purchase #4	$61.42	11.559%	$68.5195	$68.52	$68.50	$68.50
Purchase #5	$153.91	13.424%	$174.5709	$174.57	$174.55	$174.60
Purchase #6	$108.50	3.408%	$112.1977	$112.20	$112.20	$112.20
Purchase #7	$248.37	10.128%	$273.5249	$273.52	$273.50	$273.50
7 purchase totals =	$933.24		$1,013.3209	$1,013.32	$1,013.25	$1,013.30