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	$198.56	6.418%	$211.3036	$211.30	$211.30	$211.30
Purchase #2	$214.45	12.554%	$241.3721	$241.37	$241.35	$241.40
Purchase #3	$171.72	10.314%	$189.4312	$189.43	$189.45	$189.40
Purchase #4	$123.38	7.599%	$132.7556	$132.76	$132.75	$132.80
Purchase #5	$13.44	13.736%	$15.2861	$15.29	$15.30	$15.30
Purchase #6	$203.89	3.114%	$210.2391	$210.24	$210.25	$210.20
Purchase #7	$160.60	3.242%	$165.8067	$165.81	$165.80	$165.80
7 purchase totals =	$1,086.04		$1,166.1944	$1,166.20	$1,166.20	$1,166.20