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	$217.65	10.611%	$240.7448	$240.74	$240.75	$240.70
Purchase #2	$170.92	11.251%	$190.1502	$190.15	$190.15	$190.20
Purchase #3	$66.94	10.599%	$74.035	$74.04	$74.05	$74.00
Purchase #4	$35.55	6.118%	$37.7249	$37.72	$37.70	$37.70
Purchase #5	$134.89	7.863%	$145.4964	$145.50	$145.50	$145.50
Purchase #6	$135.96	10.803%	$150.6478	$150.65	$150.65	$150.60
Purchase #7	$38.47	11.825%	$43.0191	$43.02	$43.00	$43.00
7 purchase totals =	$800.38		$881.8182	$881.82	$881.80	$881.70