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	$85.34	6.123%	$90.5654	$90.57	$90.55	$90.60
Purchase #2	$95.97	9.107%	$104.71	$104.71	$104.70	$104.70
Purchase #3	$102.83	8.587%	$111.66	$111.66	$111.65	$111.70
Purchase #4	$163.38	9.244%	$178.4828	$178.48	$178.50	$178.50
Purchase #5	$205.63	10.541%	$227.3055	$227.31	$227.30	$227.30
Purchase #6	$120.48	5.578%	$127.2004	$127.20	$127.20	$127.20
Purchase #7	$163.77	4.611%	$171.3214	$171.32	$171.30	$171.30
7 purchase totals =	$937.40		$1,011.2455	$1,011.25	$1,011.20	$1,011.30