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	$176.94	6.570%	$188.565	$188.57	$188.55	$188.60
Purchase #2	$248.71	8.514%	$269.8852	$269.89	$269.90	$269.90
Purchase #3	$85.30	10.537%	$94.2881	$94.29	$94.30	$94.30
Purchase #4	$77.66	5.772%	$82.1425	$82.14	$82.15	$82.10
Purchase #5	$183.31	12.320%	$205.8938	$205.89	$205.90	$205.90
Purchase #6	$169.82	10.752%	$188.079	$188.08	$188.10	$188.10
Purchase #7	$41.72	8.211%	$45.1456	$45.15	$45.15	$45.10
7 purchase totals =	$983.46		$1,073.9992	$1,074.01	$1,074.05	$1,074.00