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	$59.59	10.617%	$65.9167	$65.92	$65.90	$65.90
Purchase #2	$235.62	8.586%	$255.8503	$255.85	$255.85	$255.90
Purchase #3	$12.79	8.113%	$13.8277	$13.83	$13.85	$13.80
Purchase #4	$83.66	3.121%	$86.271	$86.27	$86.25	$86.30
Purchase #5	$69.99	10.664%	$77.4537	$77.45	$77.45	$77.50
Purchase #6	$185.77	5.142%	$195.3223	$195.32	$195.30	$195.30
Purchase #7	$245.54	7.760%	$264.5939	$264.59	$264.60	$264.60
7 purchase totals =	$892.96		$959.2356	$959.23	$959.20	$959.30