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	$10.46	12.537%	$11.7714	$11.77	$11.75	$11.80
Purchase #2	$110.83	6.559%	$118.0993	$118.10	$118.10	$118.10
Purchase #3	$157.97	4.116%	$164.472	$164.47	$164.45	$164.50
Purchase #4	$96.42	4.728%	$100.9787	$100.98	$101.00	$101.00
Purchase #5	$249.42	6.287%	$265.101	$265.10	$265.10	$265.10
Purchase #6	$75.25	13.141%	$85.1386	$85.14	$85.15	$85.10
Purchase #7	$41.75	4.378%	$43.5778	$43.58	$43.60	$43.60
7 purchase totals =	$742.10		$789.1388	$789.14	$789.15	$789.20