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	$139.92	5.784%	$148.013	$148.01	$148.00	$148.00
Purchase #2	$151.35	13.347%	$171.5507	$171.55	$171.55	$171.60
Purchase #3	$66.36	7.758%	$71.5082	$71.51	$71.50	$71.50
Purchase #4	$240.46	8.380%	$260.6105	$260.61	$260.60	$260.60
Purchase #5	$131.52	4.102%	$136.915	$136.92	$136.90	$136.90
Purchase #6	$114.70	5.244%	$120.7149	$120.71	$120.70	$120.70
Purchase #7	$166.39	3.784%	$172.6862	$172.69	$172.70	$172.70
7 purchase totals =	$1,010.70		$1,081.9985	$1,082.00	$1,081.95	$1,082.00