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	$5.31	7.866%	$5.7277	$5.73	$5.75	$5.70
Purchase #2	$89.45	6.389%	$95.165	$95.17	$95.15	$95.20
Purchase #3	$133.85	6.491%	$142.5382	$142.54	$142.55	$142.50
Purchase #4	$63.83	5.448%	$67.3075	$67.31	$67.30	$67.30
Purchase #5	$55.53	10.716%	$61.4806	$61.48	$61.50	$61.50
Purchase #6	$194.50	10.257%	$214.4499	$214.45	$214.45	$214.40
Purchase #7	$71.95	9.776%	$78.9838	$78.98	$79.00	$79.00
7 purchase totals =	$614.42		$665.6527	$665.66	$665.70	$665.60