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	$126.84	4.240%	$132.218	$132.22	$132.20	$132.20
Purchase #2	$28.77	12.274%	$32.3012	$32.30	$32.30	$32.30
Purchase #3	$205.83	6.645%	$219.5074	$219.51	$219.50	$219.50
Purchase #4	$18.77	7.585%	$20.1937	$20.19	$20.20	$20.20
Purchase #5	$42.74	5.762%	$45.2027	$45.20	$45.20	$45.20
Purchase #6	$215.64	4.627%	$225.6177	$225.62	$225.60	$225.60
Purchase #7	$78.94	13.643%	$89.7098	$89.71	$89.70	$89.70
7 purchase totals =	$717.53		$764.7505	$764.75	$764.70	$764.70