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	$151.92	8.127%	$164.2665	$164.27	$164.25	$164.30
Purchase #2	$69.88	11.473%	$77.8973	$77.90	$77.90	$77.90
Purchase #3	$66.38	13.658%	$75.4462	$75.45	$75.45	$75.40
Purchase #4	$56.93	8.296%	$61.6529	$61.65	$61.65	$61.70
Purchase #5	$66.57	8.193%	$72.0241	$72.02	$72.00	$72.00
Purchase #6	$234.63	3.525%	$242.9007	$242.90	$242.90	$242.90
Purchase #7	$139.72	3.561%	$144.6954	$144.70	$144.70	$144.70
7 purchase totals =	$786.03		$838.8831	$838.89	$838.85	$838.90