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	$210.96	13.573%	$239.5936	$239.59	$239.60	$239.60
Purchase #2	$110.83	12.729%	$124.9376	$124.94	$124.95	$124.90
Purchase #3	$19.47	7.213%	$20.8744	$20.87	$20.85	$20.90
Purchase #4	$148.75	7.538%	$159.9628	$159.96	$159.95	$160.00
Purchase #5	$191.69	7.345%	$205.7696	$205.77	$205.75	$205.80
Purchase #6	$237.95	7.849%	$256.6267	$256.63	$256.65	$256.60
Purchase #7	$128.37	10.833%	$142.2763	$142.28	$142.30	$142.30
7 purchase totals =	$1,048.02		$1,150.0410	$1,150.04	$1,150.05	$1,150.10