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	$62.69	3.244%	$64.7237	$64.72	$64.70	$64.70
Purchase #2	$138.50	9.206%	$151.2503	$151.25	$151.25	$151.30
Purchase #3	$72.29	11.102%	$80.3156	$80.32	$80.30	$80.30
Purchase #4	$100.81	7.785%	$108.6581	$108.66	$108.65	$108.70
Purchase #5	$111.86	13.340%	$126.7821	$126.78	$126.80	$126.80
Purchase #6	$91.32	6.195%	$96.9773	$96.98	$97.00	$97.00
Purchase #7	$136.84	13.768%	$155.6801	$155.68	$155.70	$155.70
7 purchase totals =	$714.31		$784.3872	$784.39	$784.40	$784.50