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	$93.83	12.669%	$105.7173	$105.72	$105.70	$105.70
Purchase #2	$224.64	8.777%	$244.3567	$244.36	$244.35	$244.40
Purchase #3	$60.78	10.122%	$66.9322	$66.93	$66.95	$66.90
Purchase #4	$69.36	13.728%	$78.8817	$78.88	$78.90	$78.90
Purchase #5	$233.86	6.524%	$249.117	$249.12	$249.10	$249.10
Purchase #6	$107.57	10.257%	$118.6035	$118.60	$118.60	$118.60
Purchase #7	$59.87	3.721%	$62.0978	$62.10	$62.10	$62.10
7 purchase totals =	$849.91		$925.7062	$925.71	$925.70	$925.70