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	$145.34	4.470%	$151.8367	$151.84	$151.85	$151.80
Purchase #2	$52.59	6.226%	$55.8643	$55.86	$55.85	$55.90
Purchase #3	$140.88	8.862%	$153.3648	$153.36	$153.35	$153.40
Purchase #4	$59.40	4.342%	$61.9791	$61.98	$62.00	$62.00
Purchase #5	$108.63	13.464%	$123.2559	$123.26	$123.25	$123.30
Purchase #6	$97.84	10.501%	$108.1142	$108.11	$108.10	$108.10
Purchase #7	$99.35	12.221%	$111.4916	$111.49	$111.50	$111.50
7 purchase totals =	$704.03		$765.9066	$765.90	$765.90	$766.00