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	$10.27	7.114%	$11.0006	$11.00	$11.00	$11.00
Purchase #2	$78.92	5.139%	$82.9757	$82.98	$83.00	$83.00
Purchase #3	$246.32	13.401%	$279.3293	$279.33	$279.35	$279.30
Purchase #4	$167.66	13.655%	$190.554	$190.55	$190.55	$190.60
Purchase #5	$37.49	4.645%	$39.2314	$39.23	$39.25	$39.20
Purchase #6	$95.75	7.587%	$103.0146	$103.01	$103.00	$103.00
Purchase #7	$31.82	11.835%	$35.5859	$35.59	$35.60	$35.60
7 purchase totals =	$668.23		$741.6915	$741.69	$741.75	$741.70