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	$118.56	4.207%	$123.5478	$123.55	$123.55	$123.50
Purchase #2	$92.63	12.629%	$104.3282	$104.33	$104.35	$104.30
Purchase #3	$140.59	8.335%	$152.3082	$152.31	$152.30	$152.30
Purchase #4	$172.88	8.818%	$188.1246	$188.12	$188.10	$188.10
Purchase #5	$194.71	7.220%	$208.7681	$208.77	$208.75	$208.80
Purchase #6	$143.56	10.477%	$158.6008	$158.60	$158.60	$158.60
Purchase #7	$80.65	3.381%	$83.3768	$83.38	$83.40	$83.40
7 purchase totals =	$943.58		$1,019.0545	$1,019.06	$1,019.05	$1,019.00