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	$101.35	5.219%	$106.6395	$106.64	$106.65	$106.60
Purchase #2	$157.82	4.531%	$164.9708	$164.97	$164.95	$165.00
Purchase #3	$144.78	8.422%	$156.9734	$156.97	$156.95	$157.00
Purchase #4	$173.37	7.850%	$186.9795	$186.98	$187.00	$187.00
Purchase #5	$155.50	10.510%	$171.8431	$171.84	$171.85	$171.80
Purchase #6	$144.72	8.178%	$156.5552	$156.56	$156.55	$156.60
Purchase #7	$65.78	9.545%	$72.0587	$72.06	$72.05	$72.10
7 purchase totals =	$943.32		$1,016.0202	$1,016.02	$1,016.00	$1,016.10