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	$205.75	6.452%	$219.025	$219.03	$219.05	$219.00
Purchase #2	$145.33	13.499%	$164.9481	$164.95	$164.95	$164.90
Purchase #3	$107.29	4.795%	$112.4346	$112.43	$112.45	$112.40
Purchase #4	$70.85	11.179%	$78.7703	$78.77	$78.75	$78.80
Purchase #5	$240.32	4.664%	$251.5285	$251.53	$251.55	$251.50
Purchase #6	$39.43	7.314%	$42.3139	$42.31	$42.30	$42.30
Purchase #7	$170.96	3.853%	$177.5471	$177.55	$177.55	$177.50
7 purchase totals =	$979.93		$1,046.5675	$1,046.57	$1,046.60	$1,046.40