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	$219.55	12.133%	$246.188	$246.19	$246.20	$246.20
Purchase #2	$47.58	6.176%	$50.5185	$50.52	$50.50	$50.50
Purchase #3	$242.88	13.390%	$275.4016	$275.40	$275.40	$275.40
Purchase #4	$169.25	6.642%	$180.4916	$180.49	$180.50	$180.50
Purchase #5	$18.59	11.862%	$20.7951	$20.80	$20.80	$20.80
Purchase #6	$114.46	4.353%	$119.4424	$119.44	$119.45	$119.40
Purchase #7	$64.60	11.829%	$72.2415	$72.24	$72.25	$72.20
7 purchase totals =	$876.91		$965.0787	$965.08	$965.10	$965.00