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	$199.72	10.585%	$220.8604	$220.86	$220.85	$220.90
Purchase #2	$77.95	7.543%	$83.8298	$83.83	$83.85	$83.80
Purchase #3	$158.95	4.636%	$166.3189	$166.32	$166.30	$166.30
Purchase #4	$116.53	5.642%	$123.1046	$123.10	$123.10	$123.10
Purchase #5	$85.52	4.686%	$89.5275	$89.53	$89.55	$89.50
Purchase #6	$210.45	12.384%	$236.5121	$236.51	$236.50	$236.50
Purchase #7	$135.71	13.422%	$153.925	$153.93	$153.95	$153.90
7 purchase totals =	$984.83		$1,074.0783	$1,074.08	$1,074.10	$1,074.00