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	$61.81	3.116%	$63.736	$63.74	$63.75	$63.70
Purchase #2	$181.83	4.388%	$189.8087	$189.81	$189.80	$189.80
Purchase #3	$164.67	6.603%	$175.5432	$175.54	$175.55	$175.50
Purchase #4	$195.45	10.429%	$215.8335	$215.83	$215.85	$215.80
Purchase #5	$19.92	10.826%	$22.0765	$22.08	$22.10	$22.10
Purchase #6	$246.48	10.327%	$271.934	$271.93	$271.95	$271.90
Purchase #7	$103.82	7.399%	$111.5016	$111.50	$111.50	$111.50
7 purchase totals =	$973.98		$1,050.4335	$1,050.43	$1,050.50	$1,050.30