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	$190.92	7.116%	$204.5059	$204.51	$204.50	$204.50
Purchase #2	$138.69	12.356%	$155.8265	$155.83	$155.85	$155.80
Purchase #3	$202.35	12.597%	$227.84	$227.84	$227.85	$227.80
Purchase #4	$201.75	12.713%	$227.3985	$227.40	$227.40	$227.40
Purchase #5	$159.32	4.457%	$166.4209	$166.42	$166.40	$166.40
Purchase #6	$55.63	7.575%	$59.844	$59.84	$59.85	$59.80
Purchase #7	$59.60	12.868%	$67.2693	$67.27	$67.25	$67.30
7 purchase totals =	$1,008.26		$1,109.1051	$1,109.11	$1,109.10	$1,109.00