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	$62.45	11.450%	$69.6005	$69.60	$69.60	$69.60
Purchase #2	$210.97	5.350%	$222.2569	$222.26	$222.25	$222.30
Purchase #3	$93.40	7.300%	$100.2182	$100.22	$100.20	$100.20
Purchase #4	$230.26	3.438%	$238.1763	$238.18	$238.20	$238.20
Purchase #5	$144.35	4.234%	$150.4618	$150.46	$150.45	$150.50
Purchase #6	$112.73	4.549%	$117.8581	$117.86	$117.85	$117.90
Purchase #7	$124.38	8.491%	$134.9411	$134.94	$134.95	$134.90
7 purchase totals =	$978.54		$1,033.5129	$1,033.52	$1,033.50	$1,033.60