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	$214.50	11.819%	$239.8518	$239.85	$239.85	$239.90
Purchase #2	$64.78	3.845%	$67.2708	$67.27	$67.25	$67.30
Purchase #3	$206.96	9.672%	$226.9772	$226.98	$227.00	$227.00
Purchase #4	$205.87	12.411%	$231.4205	$231.42	$231.40	$231.40
Purchase #5	$41.78	9.299%	$45.6651	$45.67	$45.65	$45.70
Purchase #6	$99.49	9.853%	$109.2927	$109.29	$109.30	$109.30
Purchase #7	$74.70	11.651%	$83.4033	$83.40	$83.40	$83.40
7 purchase totals =	$908.08		$1,003.8814	$1,003.88	$1,003.85	$1,004.00