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	$233.25	4.401%	$243.5153	$243.52	$243.50	$243.50
Purchase #2	$61.46	10.262%	$67.767	$67.77	$67.75	$67.80
Purchase #3	$163.67	11.418%	$182.3578	$182.36	$182.35	$182.40
Purchase #4	$115.35	13.849%	$131.3248	$131.32	$131.30	$131.30
Purchase #5	$229.27	8.422%	$248.5791	$248.58	$248.60	$248.60
Purchase #6	$111.77	10.424%	$123.4209	$123.42	$123.40	$123.40
Purchase #7	$165.29	13.681%	$187.9033	$187.90	$187.90	$187.90
7 purchase totals =	$1,080.06		$1,184.8682	$1,184.87	$1,184.80	$1,184.90