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	$92.39	6.642%	$98.5265	$98.53	$98.55	$98.50
Purchase #2	$184.93	6.270%	$196.5251	$196.53	$196.55	$196.50
Purchase #3	$108.81	13.865%	$123.8965	$123.90	$123.90	$123.90
Purchase #4	$109.74	12.858%	$123.8504	$123.85	$123.85	$123.90
Purchase #5	$35.25	5.153%	$37.0664	$37.07	$37.05	$37.10
Purchase #6	$165.85	6.173%	$176.0879	$176.09	$176.10	$176.10
Purchase #7	$16.60	4.169%	$17.2921	$17.29	$17.30	$17.30
7 purchase totals =	$713.57		$773.2449	$773.26	$773.30	$773.30