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	$101.65	8.756%	$110.5505	$110.55	$110.55	$110.60
Purchase #2	$14.73	7.330%	$15.8097	$15.81	$15.80	$15.80
Purchase #3	$108.58	3.842%	$112.7516	$112.75	$112.75	$112.80
Purchase #4	$127.72	11.607%	$142.5445	$142.54	$142.55	$142.50
Purchase #5	$154.60	12.857%	$174.4769	$174.48	$174.50	$174.50
Purchase #6	$84.56	5.578%	$89.2768	$89.28	$89.30	$89.30
Purchase #7	$107.27	8.593%	$116.4877	$116.49	$116.50	$116.50
7 purchase totals =	$699.11		$761.8977	$761.90	$761.95	$762.00