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	$48.98	8.312%	$53.0512	$53.05	$53.05	$53.10
Purchase #2	$51.89	6.402%	$55.212	$55.21	$55.20	$55.20
Purchase #3	$169.99	13.273%	$192.5528	$192.55	$192.55	$192.60
Purchase #4	$234.41	10.749%	$259.6067	$259.61	$259.60	$259.60
Purchase #5	$128.83	10.670%	$142.5762	$142.58	$142.60	$142.60
Purchase #6	$222.88	12.511%	$250.7645	$250.76	$250.75	$250.80
Purchase #7	$134.65	6.635%	$143.584	$143.58	$143.60	$143.60
7 purchase totals =	$991.63		$1,097.3474	$1,097.34	$1,097.35	$1,097.50