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	$95.46	3.292%	$98.6025	$98.60	$98.60	$98.60
Purchase #2	$154.65	3.344%	$159.8215	$159.82	$159.80	$159.80
Purchase #3	$38.42	12.188%	$43.1026	$43.10	$43.10	$43.10
Purchase #4	$153.47	8.806%	$166.9846	$166.98	$167.00	$167.00
Purchase #5	$80.65	10.440%	$89.0699	$89.07	$89.05	$89.10
Purchase #6	$29.55	4.664%	$30.9282	$30.93	$30.95	$30.90
Purchase #7	$190.93	5.240%	$200.9347	$200.93	$200.95	$200.90
7 purchase totals =	$743.13		$789.4440	$789.43	$789.45	$789.40