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	$38.85	3.629%	$40.2599	$40.26	$40.25	$40.30
Purchase #2	$48.90	9.670%	$53.6286	$53.63	$53.65	$53.60
Purchase #3	$80.69	10.830%	$89.4287	$89.43	$89.45	$89.40
Purchase #4	$243.34	10.462%	$268.7982	$268.80	$268.80	$268.80
Purchase #5	$246.39	9.457%	$269.6911	$269.69	$269.70	$269.70
Purchase #6	$144.81	5.381%	$152.6022	$152.60	$152.60	$152.60
Purchase #7	$191.97	10.353%	$211.8447	$211.84	$211.85	$211.80
7 purchase totals =	$994.95		$1,086.2534	$1,086.25	$1,086.30	$1,086.20