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	$194.63	10.781%	$215.6131	$215.61	$215.60	$215.60
Purchase #2	$128.76	4.642%	$134.737	$134.74	$134.75	$134.70
Purchase #3	$239.90	9.607%	$262.9472	$262.95	$262.95	$262.90
Purchase #4	$105.33	10.677%	$116.5761	$116.58	$116.60	$116.60
Purchase #5	$57.71	13.703%	$65.618	$65.62	$65.60	$65.60
Purchase #6	$105.31	5.151%	$110.7345	$110.73	$110.75	$110.70
Purchase #7	$105.72	5.170%	$111.1857	$111.19	$111.20	$111.20
7 purchase totals =	$937.36		$1,017.4116	$1,017.42	$1,017.45	$1,017.30