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	$167.96	9.839%	$184.4856	$184.49	$184.50	$184.50
Purchase #2	$36.34	12.268%	$40.7982	$40.80	$40.80	$40.80
Purchase #3	$175.67	7.398%	$188.6661	$188.67	$188.65	$188.70
Purchase #4	$109.61	6.706%	$116.9604	$116.96	$116.95	$117.00
Purchase #5	$127.51	9.662%	$139.83	$139.83	$139.85	$139.80
Purchase #6	$127.74	13.214%	$144.6196	$144.62	$144.60	$144.60
Purchase #7	$137.33	9.330%	$150.1429	$150.14	$150.15	$150.10
7 purchase totals =	$882.16		$965.5028	$965.51	$965.50	$965.50