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	$245.61	4.369%	$256.3407	$256.34	$256.35	$256.30
Purchase #2	$26.77	10.556%	$29.5958	$29.60	$29.60	$29.60
Purchase #3	$198.77	8.164%	$214.9976	$215.00	$215.00	$215.00
Purchase #4	$140.60	9.413%	$153.8347	$153.83	$153.85	$153.80
Purchase #5	$57.27	8.293%	$62.0194	$62.02	$62.00	$62.00
Purchase #6	$48.78	10.611%	$53.956	$53.96	$53.95	$54.00
Purchase #7	$53.59	6.661%	$57.1596	$57.16	$57.15	$57.20
7 purchase totals =	$771.39		$827.9038	$827.91	$827.90	$827.90