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	$112.39	4.172%	$117.0789	$117.08	$117.10	$117.10
Purchase #2	$139.79	4.292%	$145.7898	$145.79	$145.80	$145.80
Purchase #3	$154.31	13.807%	$175.6156	$175.62	$175.60	$175.60
Purchase #4	$60.39	4.676%	$63.2138	$63.21	$63.20	$63.20
Purchase #5	$6.58	6.573%	$7.0125	$7.01	$7.00	$7.00
Purchase #6	$48.37	10.821%	$53.6041	$53.60	$53.60	$53.60
Purchase #7	$119.89	3.225%	$123.7565	$123.76	$123.75	$123.80
7 purchase totals =	$641.72		$686.0712	$686.07	$686.05	$686.10