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	$80.42	5.651%	$84.9645	$84.96	$84.95	$85.00
Purchase #2	$73.38	7.359%	$78.78	$78.78	$78.80	$78.80
Purchase #3	$40.44	5.325%	$42.5934	$42.59	$42.60	$42.60
Purchase #4	$223.59	11.611%	$249.551	$249.55	$249.55	$249.60
Purchase #5	$44.90	13.211%	$50.8317	$50.83	$50.85	$50.80
Purchase #6	$230.47	11.446%	$256.8496	$256.85	$256.85	$256.80
Purchase #7	$239.91	11.130%	$266.612	$266.61	$266.60	$266.60
7 purchase totals =	$933.11		$1,030.1822	$1,030.17	$1,030.20	$1,030.20