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	$160.95	13.215%	$182.2195	$182.22	$182.20	$182.20
Purchase #2	$218.29	12.597%	$245.788	$245.79	$245.80	$245.80
Purchase #3	$70.71	10.753%	$78.3134	$78.31	$78.30	$78.30
Purchase #4	$91.31	11.552%	$101.8581	$101.86	$101.85	$101.90
Purchase #5	$123.35	3.773%	$128.004	$128.00	$128.00	$128.00
Purchase #6	$43.28	6.493%	$46.0902	$46.09	$46.10	$46.10
Purchase #7	$119.62	3.247%	$123.5041	$123.50	$123.50	$123.50
7 purchase totals =	$827.51		$905.7773	$905.77	$905.75	$905.80