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	$45.69	5.734%	$48.3099	$48.31	$48.30	$48.30
Purchase #2	$57.86	4.560%	$60.4984	$60.50	$60.50	$60.50
Purchase #3	$108.87	3.603%	$112.7926	$112.79	$112.80	$112.80
Purchase #4	$101.43	7.487%	$109.0241	$109.02	$109.00	$109.00
Purchase #5	$37.45	9.293%	$40.9302	$40.93	$40.95	$40.90
Purchase #6	$154.55	11.655%	$172.5628	$172.56	$172.55	$172.60
Purchase #7	$155.73	6.226%	$165.4257	$165.43	$165.45	$165.40
7 purchase totals =	$661.58		$709.5437	$709.54	$709.55	$709.50