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	$139.33	9.204%	$152.1539	$152.15	$152.15	$152.20
Purchase #2	$116.26	7.709%	$125.2225	$125.22	$125.20	$125.20
Purchase #3	$20.97	13.860%	$23.8764	$23.88	$23.90	$23.90
Purchase #4	$98.78	13.219%	$111.8377	$111.84	$111.85	$111.80
Purchase #5	$60.45	11.715%	$67.5317	$67.53	$67.55	$67.50
Purchase #6	$68.56	5.442%	$72.291	$72.29	$72.30	$72.30
Purchase #7	$103.35	8.617%	$112.2557	$112.26	$112.25	$112.30
7 purchase totals =	$607.70		$665.1689	$665.17	$665.20	$665.20