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	$210.62	6.555%	$224.4261	$224.43	$224.45	$224.40
Purchase #2	$97.59	13.595%	$110.8574	$110.86	$110.85	$110.90
Purchase #3	$120.38	9.443%	$131.7475	$131.75	$131.75	$131.70
Purchase #4	$89.42	3.319%	$92.3878	$92.39	$92.40	$92.40
Purchase #5	$235.50	9.383%	$257.597	$257.60	$257.60	$257.60
Purchase #6	$113.57	9.754%	$124.6476	$124.65	$124.65	$124.60
Purchase #7	$121.48	8.565%	$131.8848	$131.88	$131.90	$131.90
7 purchase totals =	$988.56		$1,073.5482	$1,073.56	$1,073.60	$1,073.50