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	$238.73	4.451%	$249.3559	$249.36	$249.35	$249.40
Purchase #2	$162.32	11.440%	$180.8894	$180.89	$180.90	$180.90
Purchase #3	$9.96	3.486%	$10.3072	$10.31	$10.30	$10.30
Purchase #4	$38.47	6.455%	$40.9532	$40.95	$40.95	$41.00
Purchase #5	$214.77	5.149%	$225.8285	$225.83	$225.85	$225.80
Purchase #6	$180.96	10.626%	$200.1888	$200.19	$200.20	$200.20
Purchase #7	$119.96	3.803%	$124.5221	$124.52	$124.50	$124.50
7 purchase totals =	$965.17		$1,032.0451	$1,032.05	$1,032.05	$1,032.10