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	$153.94	6.764%	$164.3525	$164.35	$164.35	$164.40
Purchase #2	$6.87	5.821%	$7.2699	$7.27	$7.25	$7.30
Purchase #3	$139.57	3.386%	$144.2958	$144.30	$144.30	$144.30
Purchase #4	$144.87	9.373%	$158.4487	$158.45	$158.45	$158.40
Purchase #5	$93.80	6.729%	$100.1118	$100.11	$100.10	$100.10
Purchase #6	$76.93	11.631%	$85.8777	$85.88	$85.90	$85.90
Purchase #7	$211.86	11.368%	$235.9442	$235.94	$235.95	$235.90
7 purchase totals =	$827.84		$896.3006	$896.30	$896.30	$896.30