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	$114.85	3.498%	$118.8675	$118.87	$118.85	$118.90
Purchase #2	$226.63	12.433%	$254.8069	$254.81	$254.80	$254.80
Purchase #3	$175.88	3.843%	$182.6391	$182.64	$182.65	$182.60
Purchase #4	$143.85	6.703%	$153.4923	$153.49	$153.50	$153.50
Purchase #5	$83.94	7.453%	$90.196	$90.20	$90.20	$90.20
Purchase #6	$146.90	7.223%	$157.5106	$157.51	$157.50	$157.50
Purchase #7	$44.85	10.184%	$49.4175	$49.42	$49.40	$49.40
7 purchase totals =	$936.90		$1,006.9299	$1,006.94	$1,006.90	$1,006.90