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	$175.62	5.582%	$185.4231	$185.42	$185.40	$185.40
Purchase #2	$112.40	12.839%	$126.831	$126.83	$126.85	$126.80
Purchase #3	$234.80	3.188%	$242.2854	$242.29	$242.30	$242.30
Purchase #4	$117.32	8.752%	$127.5878	$127.59	$127.60	$127.60
Purchase #5	$90.58	10.397%	$99.9976	$100.00	$100.00	$100.00
Purchase #6	$190.50	11.583%	$212.5656	$212.57	$212.55	$212.60
Purchase #7	$42.64	3.116%	$43.9687	$43.97	$43.95	$44.00
7 purchase totals =	$963.86		$1,038.6592	$1,038.67	$1,038.65	$1,038.70