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	$82.91	9.145%	$90.4921	$90.49	$90.50	$90.50
Purchase #2	$215.56	5.620%	$227.6745	$227.67	$227.65	$227.70
Purchase #3	$165.40	7.115%	$177.1682	$177.17	$177.15	$177.20
Purchase #4	$244.98	6.731%	$261.4696	$261.47	$261.45	$261.50
Purchase #5	$66.91	9.421%	$73.2136	$73.21	$73.20	$73.20
Purchase #6	$194.41	10.804%	$215.4141	$215.41	$215.40	$215.40
Purchase #7	$95.60	3.600%	$99.0416	$99.04	$99.05	$99.00
7 purchase totals =	$1,065.77		$1,144.4737	$1,144.46	$1,144.40	$1,144.50