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	$59.47	3.861%	$61.7661	$61.77	$61.75	$61.80
Purchase #2	$29.58	11.233%	$32.9027	$32.90	$32.90	$32.90
Purchase #3	$226.64	3.210%	$233.9151	$233.92	$233.90	$233.90
Purchase #4	$149.84	12.139%	$168.0291	$168.03	$168.05	$168.00
Purchase #5	$240.82	13.271%	$272.7792	$272.78	$272.80	$272.80
Purchase #6	$62.71	9.667%	$68.7722	$68.77	$68.75	$68.80
Purchase #7	$242.37	12.631%	$272.9838	$272.98	$273.00	$273.00
7 purchase totals =	$1,011.43		$1,111.1482	$1,111.15	$1,111.15	$1,111.20