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	$70.91	10.541%	$78.3846	$78.38	$78.40	$78.40
Purchase #2	$112.29	5.497%	$118.4626	$118.46	$118.45	$118.50
Purchase #3	$91.42	7.558%	$98.3295	$98.33	$98.35	$98.30
Purchase #4	$232.93	11.540%	$259.8101	$259.81	$259.80	$259.80
Purchase #5	$203.70	8.110%	$220.2201	$220.22	$220.20	$220.20
Purchase #6	$166.65	3.480%	$172.4494	$172.45	$172.45	$172.40
Purchase #7	$78.42	3.595%	$81.2392	$81.24	$81.25	$81.20
7 purchase totals =	$956.32		$1,028.8955	$1,028.89	$1,028.90	$1,028.80