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	$145.82	13.392%	$165.3482	$165.35	$165.35	$165.30
Purchase #2	$196.64	10.795%	$217.8673	$217.87	$217.85	$217.90
Purchase #3	$234.33	10.264%	$258.3816	$258.38	$258.40	$258.40
Purchase #4	$103.92	12.166%	$116.5629	$116.56	$116.55	$116.60
Purchase #5	$36.69	4.212%	$38.2354	$38.24	$38.25	$38.20
Purchase #6	$50.88	8.716%	$55.3147	$55.31	$55.30	$55.30
Purchase #7	$206.36	7.395%	$221.6203	$221.62	$221.60	$221.60
7 purchase totals =	$974.64		$1,073.3304	$1,073.33	$1,073.30	$1,073.30