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	$210.38	9.133%	$229.594	$229.59	$229.60	$229.60
Purchase #2	$88.47	13.134%	$100.0896	$100.09	$100.10	$100.10
Purchase #3	$59.26	8.163%	$64.0974	$64.10	$64.10	$64.10
Purchase #4	$208.66	7.172%	$223.6251	$223.63	$223.65	$223.60
Purchase #5	$89.60	3.333%	$92.5864	$92.59	$92.60	$92.60
Purchase #6	$99.76	4.462%	$104.2113	$104.21	$104.20	$104.20
Purchase #7	$131.48	9.763%	$144.3164	$144.32	$144.30	$144.30
7 purchase totals =	$887.61		$958.5202	$958.53	$958.55	$958.50