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	$238.44	4.339%	$248.7859	$248.79	$248.80	$248.80
Purchase #2	$164.25	6.656%	$175.1825	$175.18	$175.20	$175.20
Purchase #3	$6.27	11.522%	$6.9924	$6.99	$7.00	$7.00
Purchase #4	$41.28	6.730%	$44.0581	$44.06	$44.05	$44.10
Purchase #5	$172.43	5.270%	$181.5171	$181.52	$181.50	$181.50
Purchase #6	$175.28	12.337%	$196.9043	$196.90	$196.90	$196.90
Purchase #7	$154.34	5.423%	$162.7099	$162.71	$162.70	$162.70
7 purchase totals =	$952.29		$1,016.1502	$1,016.15	$1,016.15	$1,016.20