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	$146.89	4.606%	$153.6558	$153.66	$153.65	$153.70
Purchase #2	$89.88	10.438%	$99.2617	$99.26	$99.25	$99.30
Purchase #3	$7.84	9.629%	$8.5949	$8.59	$8.60	$8.60
Purchase #4	$161.55	6.222%	$171.6016	$171.60	$171.60	$171.60
Purchase #5	$58.57	13.458%	$66.4524	$66.45	$66.45	$66.50
Purchase #6	$248.98	4.367%	$259.853	$259.85	$259.85	$259.90
Purchase #7	$135.76	5.688%	$143.482	$143.48	$143.50	$143.50
7 purchase totals =	$849.47		$902.9014	$902.89	$902.90	$903.10