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	$112.26	9.550%	$122.9808	$122.98	$123.00	$123.00
Purchase #2	$232.41	7.129%	$248.9785	$248.98	$249.00	$249.00
Purchase #3	$56.85	7.754%	$61.2581	$61.26	$61.25	$61.30
Purchase #4	$56.64	10.483%	$62.5776	$62.58	$62.60	$62.60
Purchase #5	$104.39	12.114%	$117.0358	$117.04	$117.05	$117.00
Purchase #6	$95.73	3.804%	$99.3716	$99.37	$99.35	$99.40
Purchase #7	$28.73	13.630%	$32.6459	$32.65	$32.65	$32.60
7 purchase totals =	$687.01		$744.8483	$744.86	$744.90	$744.90