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	$96.66	5.142%	$101.6303	$101.63	$101.65	$101.60
Purchase #2	$85.48	5.386%	$90.084	$90.08	$90.10	$90.10
Purchase #3	$43.57	6.756%	$46.5136	$46.51	$46.50	$46.50
Purchase #4	$92.95	11.477%	$103.6179	$103.62	$103.60	$103.60
Purchase #5	$198.54	5.795%	$210.0454	$210.05	$210.05	$210.00
Purchase #6	$220.35	12.360%	$247.5853	$247.59	$247.60	$247.60
Purchase #7	$150.40	4.364%	$156.9635	$156.96	$156.95	$157.00
7 purchase totals =	$887.95		$956.4400	$956.44	$956.45	$956.40