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	$53.48	6.484%	$56.9476	$56.95	$56.95	$56.90
Purchase #2	$28.89	10.525%	$31.9307	$31.93	$31.95	$31.90
Purchase #3	$233.31	12.311%	$262.0328	$262.03	$262.05	$262.00
Purchase #4	$160.80	6.366%	$171.0365	$171.04	$171.05	$171.00
Purchase #5	$114.60	11.583%	$127.8741	$127.87	$127.85	$127.90
Purchase #6	$181.96	9.827%	$199.8412	$199.84	$199.85	$199.80
Purchase #7	$114.72	7.727%	$123.5844	$123.58	$123.60	$123.60
7 purchase totals =	$887.76		$973.2473	$973.24	$973.30	$973.10