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	$143.73	8.422%	$155.8349	$155.83	$155.85	$155.80
Purchase #2	$219.72	13.350%	$249.0526	$249.05	$249.05	$249.10
Purchase #3	$141.33	12.271%	$158.6726	$158.67	$158.65	$158.70
Purchase #4	$191.80	11.815%	$214.4612	$214.46	$214.45	$214.50
Purchase #5	$168.47	7.112%	$180.4516	$180.45	$180.45	$180.50
Purchase #6	$192.26	4.249%	$200.4291	$200.43	$200.45	$200.40
Purchase #7	$31.44	6.687%	$33.5424	$33.54	$33.55	$33.50
7 purchase totals =	$1,088.75		$1,192.4444	$1,192.43	$1,192.45	$1,192.50