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	$212.74	13.711%	$241.9088	$241.91	$241.90	$241.90
Purchase #2	$49.30	9.119%	$53.7957	$53.80	$53.80	$53.80
Purchase #3	$168.59	7.417%	$181.0943	$181.09	$181.10	$181.10
Purchase #4	$81.65	6.477%	$86.9385	$86.94	$86.95	$86.90
Purchase #5	$123.58	3.503%	$127.909	$127.91	$127.90	$127.90
Purchase #6	$50.66	3.328%	$52.346	$52.35	$52.35	$52.30
Purchase #7	$31.51	3.414%	$32.5858	$32.59	$32.60	$32.60
7 purchase totals =	$718.03		$776.5781	$776.59	$776.60	$776.50