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	$229.27	10.476%	$253.2883	$253.29	$253.30	$253.30
Purchase #2	$76.73	5.636%	$81.0545	$81.05	$81.05	$81.10
Purchase #3	$131.64	8.382%	$142.6741	$142.67	$142.65	$142.70
Purchase #4	$32.94	3.472%	$34.0837	$34.08	$34.10	$34.10
Purchase #5	$238.52	6.571%	$254.1931	$254.19	$254.20	$254.20
Purchase #6	$210.35	13.601%	$238.9597	$238.96	$238.95	$239.00
Purchase #7	$52.92	7.412%	$56.8424	$56.84	$56.85	$56.80
7 purchase totals =	$972.37		$1,061.0958	$1,061.08	$1,061.10	$1,061.20