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	$95.33	10.453%	$105.2948	$105.29	$105.30	$105.30
Purchase #2	$77.70	9.818%	$85.3286	$85.33	$85.35	$85.30
Purchase #3	$97.92	6.164%	$103.9558	$103.96	$103.95	$104.00
Purchase #4	$10.57	11.354%	$11.7701	$11.77	$11.75	$11.80
Purchase #5	$87.33	5.751%	$92.3523	$92.35	$92.35	$92.40
Purchase #6	$18.45	4.702%	$19.3175	$19.32	$19.30	$19.30
Purchase #7	$224.80	3.870%	$233.4998	$233.50	$233.50	$233.50
7 purchase totals =	$612.10		$651.5189	$651.52	$651.50	$651.60