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	$137.97	3.534%	$142.8459	$142.85	$142.85	$142.80
Purchase #2	$250.66	12.286%	$281.4561	$281.46	$281.45	$281.50
Purchase #3	$143.90	3.321%	$148.6789	$148.68	$148.70	$148.70
Purchase #4	$92.48	3.660%	$95.8648	$95.86	$95.85	$95.90
Purchase #5	$132.78	13.559%	$150.7836	$150.78	$150.80	$150.80
Purchase #6	$211.65	8.305%	$229.2275	$229.23	$229.25	$229.20
Purchase #7	$48.42	10.550%	$53.5283	$53.53	$53.55	$53.50
7 purchase totals =	$1,017.86		$1,102.3851	$1,102.39	$1,102.45	$1,102.40