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	$126.38	10.450%	$139.5867	$139.59	$139.60	$139.60
Purchase #2	$160.30	7.719%	$172.6736	$172.67	$172.65	$172.70
Purchase #3	$169.28	7.615%	$182.1707	$182.17	$182.15	$182.20
Purchase #4	$84.83	5.220%	$89.2581	$89.26	$89.25	$89.30
Purchase #5	$133.42	11.272%	$148.4591	$148.46	$148.45	$148.50
Purchase #6	$189.29	7.540%	$203.5625	$203.56	$203.55	$203.60
Purchase #7	$209.77	4.571%	$219.3586	$219.36	$219.35	$219.40
7 purchase totals =	$1,073.27		$1,155.0693	$1,155.07	$1,155.00	$1,155.30