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	$88.70	8.121%	$95.9033	$95.90	$95.90	$95.90
Purchase #2	$82.57	3.847%	$85.7465	$85.75	$85.75	$85.70
Purchase #3	$187.78	12.645%	$211.5248	$211.52	$211.50	$211.50
Purchase #4	$66.38	12.842%	$74.9045	$74.90	$74.90	$74.90
Purchase #5	$95.89	4.423%	$100.1312	$100.13	$100.15	$100.10
Purchase #6	$215.93	6.770%	$230.5485	$230.55	$230.55	$230.50
Purchase #7	$75.88	3.198%	$78.3066	$78.31	$78.30	$78.30
7 purchase totals =	$813.13		$877.0654	$877.06	$877.05	$876.90