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	$152.92	6.189%	$162.3842	$162.38	$162.40	$162.40
Purchase #2	$67.55	5.852%	$71.503	$71.50	$71.50	$71.50
Purchase #3	$245.56	13.651%	$279.0814	$279.08	$279.10	$279.10
Purchase #4	$197.48	10.570%	$218.3536	$218.35	$218.35	$218.40
Purchase #5	$238.40	6.346%	$253.5289	$253.53	$253.55	$253.50
Purchase #6	$127.56	7.116%	$136.6372	$136.64	$136.65	$136.60
Purchase #7	$37.45	3.149%	$38.6293	$38.63	$38.65	$38.60
7 purchase totals =	$1,066.92		$1,160.1176	$1,160.11	$1,160.20	$1,160.10