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	$160.80	10.588%	$177.8255	$177.83	$177.85	$177.80
Purchase #2	$41.80	9.793%	$45.8935	$45.89	$45.90	$45.90
Purchase #3	$85.48	4.423%	$89.2608	$89.26	$89.25	$89.30
Purchase #4	$170.88	11.525%	$190.5739	$190.57	$190.55	$190.60
Purchase #5	$70.32	8.676%	$76.421	$76.42	$76.40	$76.40
Purchase #6	$101.99	13.168%	$115.42	$115.42	$115.40	$115.40
Purchase #7	$34.69	6.672%	$37.0045	$37.00	$37.00	$37.00
7 purchase totals =	$665.96		$732.3992	$732.39	$732.35	$732.40