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	$100.29	6.836%	$107.1458	$107.15	$107.15	$107.10
Purchase #2	$137.55	11.855%	$153.8566	$153.86	$153.85	$153.90
Purchase #3	$156.67	7.241%	$168.0145	$168.01	$168.00	$168.00
Purchase #4	$9.61	7.422%	$10.3233	$10.32	$10.30	$10.30
Purchase #5	$153.34	8.537%	$166.4306	$166.43	$166.45	$166.40
Purchase #6	$86.56	3.201%	$89.3308	$89.33	$89.35	$89.30
Purchase #7	$70.47	5.638%	$74.4431	$74.44	$74.45	$74.40
7 purchase totals =	$714.49		$769.5447	$769.54	$769.55	$769.40