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	$54.61	5.243%	$57.4732	$57.47	$57.45	$57.50
Purchase #2	$143.25	6.526%	$152.5985	$152.60	$152.60	$152.60
Purchase #3	$97.89	12.592%	$110.2163	$110.22	$110.20	$110.20
Purchase #4	$247.29	13.186%	$279.8977	$279.90	$279.90	$279.90
Purchase #5	$208.81	4.588%	$218.3902	$218.39	$218.40	$218.40
Purchase #6	$85.63	10.166%	$94.3351	$94.34	$94.35	$94.30
Purchase #7	$176.84	3.124%	$182.3645	$182.36	$182.35	$182.40
7 purchase totals =	$1,014.32		$1,095.2755	$1,095.28	$1,095.25	$1,095.30