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	$37.91	8.392%	$41.0914	$41.09	$41.10	$41.10
Purchase #2	$172.45	5.371%	$181.7123	$181.71	$181.70	$181.70
Purchase #3	$98.74	13.320%	$111.8922	$111.89	$111.90	$111.90
Purchase #4	$56.47	13.316%	$63.9895	$63.99	$64.00	$64.00
Purchase #5	$178.86	4.787%	$187.422	$187.42	$187.40	$187.40
Purchase #6	$208.34	5.147%	$219.0633	$219.06	$219.05	$219.10
Purchase #7	$243.68	5.429%	$256.9094	$256.91	$256.90	$256.90
7 purchase totals =	$996.45		$1,062.0801	$1,062.07	$1,062.05	$1,062.10