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	$134.98	4.607%	$141.1985	$141.20	$141.20	$141.20
Purchase #2	$138.71	5.449%	$146.2683	$146.27	$146.25	$146.30
Purchase #3	$148.81	13.212%	$168.4708	$168.47	$168.45	$168.50
Purchase #4	$248.76	11.587%	$277.5838	$277.58	$277.60	$277.60
Purchase #5	$86.27	4.873%	$90.4739	$90.47	$90.45	$90.50
Purchase #6	$60.60	13.251%	$68.6301	$68.63	$68.65	$68.60
Purchase #7	$182.53	12.820%	$205.9303	$205.93	$205.95	$205.90
7 purchase totals =	$1,000.66		$1,098.5557	$1,098.55	$1,098.55	$1,098.60