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	$61.97	5.668%	$65.4825	$65.48	$65.50	$65.50
Purchase #2	$133.66	6.475%	$142.3145	$142.31	$142.30	$142.30
Purchase #3	$183.27	4.680%	$191.847	$191.85	$191.85	$191.80
Purchase #4	$76.48	3.196%	$78.9243	$78.92	$78.90	$78.90
Purchase #5	$107.26	7.841%	$115.6703	$115.67	$115.65	$115.70
Purchase #6	$95.82	11.123%	$106.4781	$106.48	$106.50	$106.50
Purchase #7	$42.32	4.136%	$44.0704	$44.07	$44.05	$44.10
7 purchase totals =	$700.78		$744.7871	$744.78	$744.75	$744.80