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	$42.73	13.857%	$48.6511	$48.65	$48.65	$48.70
Purchase #2	$180.43	12.761%	$203.4547	$203.45	$203.45	$203.50
Purchase #3	$113.89	3.854%	$118.2793	$118.28	$118.30	$118.30
Purchase #4	$62.27	4.862%	$65.2976	$65.30	$65.30	$65.30
Purchase #5	$210.98	4.236%	$219.9171	$219.92	$219.90	$219.90
Purchase #6	$226.52	12.856%	$255.6414	$255.64	$255.65	$255.60
Purchase #7	$47.96	12.463%	$53.9373	$53.94	$53.95	$53.90
7 purchase totals =	$884.78		$965.1785	$965.18	$965.20	$965.20