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	$214.77	5.722%	$227.0591	$227.06	$227.05	$227.10
Purchase #2	$165.78	13.801%	$188.6593	$188.66	$188.65	$188.70
Purchase #3	$143.82	8.782%	$156.4503	$156.45	$156.45	$156.50
Purchase #4	$149.82	10.844%	$166.0665	$166.07	$166.05	$166.10
Purchase #5	$140.38	10.440%	$155.0357	$155.04	$155.05	$155.00
Purchase #6	$19.67	6.841%	$21.0156	$21.02	$21.00	$21.00
Purchase #7	$182.36	8.711%	$198.2454	$198.25	$198.25	$198.20
7 purchase totals =	$1,016.60		$1,112.5319	$1,112.55	$1,112.50	$1,112.60