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	$120.50	9.618%	$132.0897	$132.09	$132.10	$132.10
Purchase #2	$212.54	7.808%	$229.1351	$229.14	$229.15	$229.10
Purchase #3	$144.92	5.472%	$152.85	$152.85	$152.85	$152.90
Purchase #4	$43.86	10.814%	$48.603	$48.60	$48.60	$48.60
Purchase #5	$64.29	4.648%	$67.2782	$67.28	$67.30	$67.30
Purchase #6	$190.31	4.238%	$198.3753	$198.38	$198.40	$198.40
Purchase #7	$174.71	3.665%	$181.1131	$181.11	$181.10	$181.10
7 purchase totals =	$951.13		$1,009.4444	$1,009.45	$1,009.50	$1,009.50