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	$85.82	3.719%	$89.0116	$89.01	$89.00	$89.00
Purchase #2	$96.30	4.439%	$100.5748	$100.57	$100.55	$100.60
Purchase #3	$181.59	10.390%	$200.4572	$200.46	$200.45	$200.50
Purchase #4	$32.91	10.520%	$36.3721	$36.37	$36.35	$36.40
Purchase #5	$196.46	7.553%	$211.2986	$211.30	$211.30	$211.30
Purchase #6	$214.57	4.490%	$224.2042	$224.20	$224.20	$224.20
Purchase #7	$164.99	9.204%	$180.1757	$180.18	$180.20	$180.20
7 purchase totals =	$972.64		$1,042.0942	$1,042.09	$1,042.05	$1,042.20