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	$144.77	9.219%	$158.1163	$158.12	$158.10	$158.10
Purchase #2	$151.52	6.459%	$161.3067	$161.31	$161.30	$161.30
Purchase #3	$25.51	3.154%	$26.3146	$26.31	$26.30	$26.30
Purchase #4	$34.25	11.860%	$38.3121	$38.31	$38.30	$38.30
Purchase #5	$136.74	13.327%	$154.9633	$154.96	$154.95	$155.00
Purchase #6	$80.60	12.752%	$90.8781	$90.88	$90.90	$90.90
Purchase #7	$72.74	12.860%	$82.0944	$82.09	$82.10	$82.10
7 purchase totals =	$646.13		$711.9855	$711.98	$711.95	$712.00