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	$85.70	12.189%	$96.146	$96.15	$96.15	$96.10
Purchase #2	$28.34	9.537%	$31.0428	$31.04	$31.05	$31.00
Purchase #3	$108.94	9.301%	$119.0725	$119.07	$119.05	$119.10
Purchase #4	$182.37	3.123%	$188.0654	$188.07	$188.05	$188.10
Purchase #5	$131.82	5.477%	$139.0398	$139.04	$139.05	$139.00
Purchase #6	$77.44	10.325%	$85.4357	$85.44	$85.45	$85.40
Purchase #7	$63.71	4.356%	$66.4852	$66.49	$66.50	$66.50
7 purchase totals =	$678.32		$725.2874	$725.30	$725.30	$725.20