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	$179.51	5.472%	$189.3328	$189.33	$189.35	$189.30
Purchase #2	$29.78	12.150%	$33.3983	$33.40	$33.40	$33.40
Purchase #3	$164.83	6.527%	$175.5885	$175.59	$175.60	$175.60
Purchase #4	$99.84	4.756%	$104.5884	$104.59	$104.60	$104.60
Purchase #5	$212.62	13.123%	$240.5221	$240.52	$240.50	$240.50
Purchase #6	$198.80	3.388%	$205.5353	$205.54	$205.55	$205.50
Purchase #7	$215.98	4.359%	$225.3946	$225.39	$225.40	$225.40
7 purchase totals =	$1,101.36		$1,174.3600	$1,174.36	$1,174.40	$1,174.30