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	$233.51	4.746%	$244.5924	$244.59	$244.60	$244.60
Purchase #2	$196.80	10.728%	$217.9127	$217.91	$217.90	$217.90
Purchase #3	$186.95	3.145%	$192.8296	$192.83	$192.85	$192.80
Purchase #4	$17.65	11.726%	$19.7196	$19.72	$19.70	$19.70
Purchase #5	$141.63	6.643%	$151.0385	$151.04	$151.05	$151.00
Purchase #6	$220.43	3.514%	$228.1759	$228.18	$228.20	$228.20
Purchase #7	$221.60	11.156%	$246.3217	$246.32	$246.30	$246.30
7 purchase totals =	$1,218.57		$1,300.5904	$1,300.59	$1,300.60	$1,300.50