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	$168.83	11.222%	$187.7761	$187.78	$187.80	$187.80
Purchase #2	$154.80	11.224%	$172.1748	$172.17	$172.15	$172.20
Purchase #3	$79.95	12.520%	$89.9597	$89.96	$89.95	$90.00
Purchase #4	$126.98	13.772%	$144.4677	$144.47	$144.45	$144.50
Purchase #5	$117.77	4.478%	$123.0437	$123.04	$123.05	$123.00
Purchase #6	$171.63	4.624%	$179.5662	$179.57	$179.55	$179.60
Purchase #7	$156.60	6.770%	$167.2018	$167.20	$167.20	$167.20
7 purchase totals =	$976.56		$1,064.1900	$1,064.19	$1,064.15	$1,064.30