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	$175.76	8.446%	$190.6047	$190.60	$190.60	$190.60
Purchase #2	$92.57	10.703%	$102.4778	$102.48	$102.50	$102.50
Purchase #3	$207.61	5.692%	$219.4272	$219.43	$219.45	$219.40
Purchase #4	$134.96	13.182%	$152.7504	$152.75	$152.75	$152.80
Purchase #5	$22.47	6.655%	$23.9654	$23.97	$23.95	$24.00
Purchase #6	$83.72	7.178%	$89.7294	$89.73	$89.75	$89.70
Purchase #7	$161.27	13.120%	$182.4286	$182.43	$182.45	$182.40
7 purchase totals =	$878.36		$961.3835	$961.39	$961.45	$961.40