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	$130.89	11.651%	$146.14	$146.14	$146.15	$146.10
Purchase #2	$31.71	5.511%	$33.4575	$33.46	$33.45	$33.50
Purchase #3	$126.89	7.647%	$136.5933	$136.59	$136.60	$136.60
Purchase #4	$103.36	13.351%	$117.1596	$117.16	$117.15	$117.20
Purchase #5	$151.71	5.369%	$159.8553	$159.86	$159.85	$159.90
Purchase #6	$123.97	3.359%	$128.1342	$128.13	$128.15	$128.10
Purchase #7	$17.44	9.709%	$19.1332	$19.13	$19.15	$19.10
7 purchase totals =	$685.97		$740.4731	$740.47	$740.50	$740.50