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	$238.90	11.201%	$265.6592	$265.66	$265.65	$265.70
Purchase #2	$19.64	5.130%	$20.6475	$20.65	$20.65	$20.60
Purchase #3	$104.72	6.192%	$111.2043	$111.20	$111.20	$111.20
Purchase #4	$58.48	8.574%	$63.4941	$63.49	$63.50	$63.50
Purchase #5	$28.56	11.224%	$31.7656	$31.77	$31.75	$31.80
Purchase #6	$167.26	12.271%	$187.7845	$187.78	$187.80	$187.80
Purchase #7	$200.77	10.689%	$222.2303	$222.23	$222.25	$222.20
7 purchase totals =	$818.33		$902.7855	$902.78	$902.80	$902.80