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	$239.73	4.815%	$251.273	$251.27	$251.25	$251.30
Purchase #2	$171.67	9.291%	$187.6199	$187.62	$187.60	$187.60
Purchase #3	$142.28	4.290%	$148.3838	$148.38	$148.40	$148.40
Purchase #4	$87.83	9.873%	$96.5015	$96.50	$96.50	$96.50
Purchase #5	$8.84	13.682%	$10.0495	$10.05	$10.05	$10.00
Purchase #6	$64.84	8.752%	$70.5148	$70.51	$70.50	$70.50
Purchase #7	$245.85	3.822%	$255.2464	$255.25	$255.25	$255.20
7 purchase totals =	$961.04		$1,019.5889	$1,019.58	$1,019.55	$1,019.50