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	$173.87	11.260%	$193.4478	$193.45	$193.45	$193.40
Purchase #2	$62.54	7.715%	$67.365	$67.37	$67.35	$67.40
Purchase #3	$162.71	11.760%	$181.8447	$181.84	$181.85	$181.80
Purchase #4	$199.87	9.712%	$219.2814	$219.28	$219.30	$219.30
Purchase #5	$222.79	13.493%	$252.8511	$252.85	$252.85	$252.90
Purchase #6	$69.69	12.668%	$78.5183	$78.52	$78.50	$78.50
Purchase #7	$154.78	6.672%	$165.1069	$165.11	$165.10	$165.10
7 purchase totals =	$1,046.25		$1,158.4152	$1,158.42	$1,158.40	$1,158.40