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	$176.55	12.613%	$198.8183	$198.82	$198.80	$198.80
Purchase #2	$20.47	6.485%	$21.7975	$21.80	$21.80	$21.80
Purchase #3	$88.99	13.370%	$100.888	$100.89	$100.90	$100.90
Purchase #4	$148.88	12.843%	$168.0007	$168.00	$168.00	$168.00
Purchase #5	$47.47	12.362%	$53.3382	$53.34	$53.35	$53.30
Purchase #6	$102.54	5.415%	$108.0925	$108.09	$108.10	$108.10
Purchase #7	$160.72	4.649%	$168.1919	$168.19	$168.20	$168.20
7 purchase totals =	$745.62		$819.1271	$819.13	$819.15	$819.10