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	$88.60	5.338%	$93.3295	$93.33	$93.35	$93.30
Purchase #2	$53.25	6.224%	$56.5643	$56.56	$56.55	$56.60
Purchase #3	$178.63	4.384%	$186.4611	$186.46	$186.45	$186.50
Purchase #4	$159.73	12.374%	$179.495	$179.50	$179.50	$179.50
Purchase #5	$195.83	12.635%	$220.5731	$220.57	$220.55	$220.60
Purchase #6	$51.52	7.404%	$55.3345	$55.33	$55.35	$55.30
Purchase #7	$231.47	13.495%	$262.7069	$262.71	$262.70	$262.70
7 purchase totals =	$959.03		$1,054.4644	$1,054.46	$1,054.45	$1,054.50