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	$116.53	5.174%	$122.5593	$122.56	$122.55	$122.60
Purchase #2	$156.75	9.245%	$171.2415	$171.24	$171.25	$171.20
Purchase #3	$15.51	6.874%	$16.5762	$16.58	$16.60	$16.60
Purchase #4	$160.87	4.752%	$168.5145	$168.51	$168.50	$168.50
Purchase #5	$19.92	8.148%	$21.5431	$21.54	$21.55	$21.50
Purchase #6	$204.88	5.289%	$215.7161	$215.72	$215.70	$215.70
Purchase #7	$68.42	5.361%	$72.088	$72.09	$72.10	$72.10
7 purchase totals =	$742.88		$788.2387	$788.24	$788.25	$788.20