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	$65.46	11.441%	$72.9493	$72.95	$72.95	$72.90
Purchase #2	$186.83	12.463%	$210.1146	$210.11	$210.10	$210.10
Purchase #3	$118.70	13.366%	$134.5654	$134.57	$134.55	$134.60
Purchase #4	$29.86	5.859%	$31.6095	$31.61	$31.60	$31.60
Purchase #5	$222.31	13.678%	$252.7176	$252.72	$252.70	$252.70
Purchase #6	$87.96	4.461%	$91.8839	$91.88	$91.90	$91.90
Purchase #7	$97.50	11.251%	$108.4697	$108.47	$108.45	$108.50
7 purchase totals =	$808.62		$902.3100	$902.31	$902.25	$902.30