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	$148.81	12.620%	$167.5898	$167.59	$167.60	$167.60
Purchase #2	$249.78	10.286%	$275.4724	$275.47	$275.45	$275.50
Purchase #3	$38.82	4.383%	$40.5215	$40.52	$40.50	$40.50
Purchase #4	$6.54	3.149%	$6.7459	$6.75	$6.75	$6.70
Purchase #5	$207.86	11.800%	$232.3875	$232.39	$232.40	$232.40
Purchase #6	$197.69	3.410%	$204.4312	$204.43	$204.45	$204.40
Purchase #7	$147.61	12.369%	$165.8679	$165.87	$165.85	$165.90
7 purchase totals =	$997.11		$1,093.0162	$1,093.02	$1,093.00	$1,093.00