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	$144.31	8.399%	$156.4306	$156.43	$156.45	$156.40
Purchase #2	$224.96	4.808%	$235.7761	$235.78	$235.80	$235.80
Purchase #3	$89.44	4.212%	$93.2072	$93.21	$93.20	$93.20
Purchase #4	$151.61	10.542%	$167.5927	$167.59	$167.60	$167.60
Purchase #5	$62.63	12.176%	$70.2558	$70.26	$70.25	$70.30
Purchase #6	$154.39	7.150%	$165.4289	$165.43	$165.45	$165.40
Purchase #7	$104.25	9.595%	$114.2528	$114.25	$114.25	$114.30
7 purchase totals =	$931.59		$1,002.9441	$1,002.95	$1,003.00	$1,003.00